PrestaShop Prices and VAT: Display, Tax Rules and EU Sales
Configure net and gross prices, unit prices and tax rules in PrestaShop. Understand EU VAT thresholds, OSS, IOSS and price-reduction references.
Configure what customers see separately from the VAT you charge and the returns you file. Set up price display, destination tax rules and the records you need for EU sales.
What we would do
Start with the shop you already run: its PrestaShop version, theme and checkout, price and exemption modules, ERP or accounting integrations, product data, dispatch locations and target markets. Ask your accountant to confirm the treatment of the supplies you actually make, then map each requirement to display, tax calculation or reporting. Keep working native settings unless a missing workflow justifies a module or theme change.
Make the change on a private staging copy with the same relevant modules and data structure. Isolate customer emails, payments, stock synchronisation and accounting exports from live systems. Save the current settings and assignments, rehearse representative orders and corrections, then plan the live switch with a named person checking the first affected orders and a documented way to restore the configuration.
| Your requirement | Start with | Evidence before changing the live shop |
|---|---|---|
| Registered trade buyers need net figures. | Native group display and the account's default-group assignment. | An approved account sees the intended view while retail and guest journeys retain clear gross prices. |
| Anonymous retail and trade visitors share the catalogue. | Clearly labelled dual prices or a display selector, with a suitable consumer default. | The chosen view remains consistent through discounts, delivery and checkout without granting exemption. |
| A destination or product is charged incorrectly. | The product's tax profile, matching destination rule, address basis and exemption settings. | An accountant-approved expected result matched to the order and invoice. |
| Figures will not reconcile for a return. | Supply classification and the export specification. | Source transactions and corrections traced to the reporting totals, with currencies kept distinct until conversion. |
| Promotions show an unsupported reference price. | Price history and the rule for that market. | The displayed comparison can be traced to eligible recorded prices. |
For gaps across account approval, trade pricing and checkout tax, the PrestaShop B2B & Wholesale Readiness Audit assesses the existing buyer journey and proposes an implementation order; your accountant decides the tax treatment.
Set net and gross display by customer group
For EU consumer offers, show the selling price including VAT and other taxes that apply, as defined in Directive 98/6/EC. For example, a EUR 100 net product with 21% VAT has a EUR 121 gross price. Disclose delivery and other additional charges clearly before purchase. Tax-exempt sellers should use wording appropriate to their actual treatment.
In PrestaShop 1.7, 8 and 9, open Shop Parameters > Customer Settings > Groups. Edit the relevant groups and set Price display method to Tax included for consumer-facing browsing. The standard Visitor, Guest and Customer groups cover different states:
| Customer state | Native group used for display |
|---|---|
| Anonymous visitor | The configured unidentified group, normally Visitor. |
| Guest-checkout account | Its default group, normally the configured Guest group. |
| Registered customer | The account's default group, normally Customer for retail accounts. |
| Approved trade customer | The selected default business group, if you have assigned one. |
The group's price_display_method uses 0 for tax included and 1 for tax excluded. Its show_prices flag controls whether prices appear at all. Group discounts are another separate setting.
PS_TAX enables tax calculation. PS_TAX_DISPLAY, exposed as the cart tax-display option, affects tax presentation in the cart. It is not the catalogue's global net/gross switch. Inspect the product page, listings, search, cart, checkout and invoices rather than judging one screen.
This read-only query shows group settings using the example prefix ps_ and language ID 1. Substitute your own values:
SELECT g.id_group, gl.name, g.price_display_method,
g.show_prices, g.reduction AS group_discount_pct
FROM ps_group g
JOIN ps_group_lang gl
ON gl.id_group = g.id_group AND gl.id_lang = 1
ORDER BY g.id_group;Show trade prices without confusing display and exemption
Create a business group with Tax excluded display when that suits your trade audience. Add the approved customer to it and set it as the account's default group. Membership alone does not select the native display method. Native settings are sufficient when approved accounts only need net display. Keep retail-facing groups gross and label net figures clearly.
Net display does not itself remove VAT. A trade customer can see EUR 100 net and still owe EUR 119 at checkout when 19% tax applies. Input VAT recovery also depends on the buyer's status, activities and deduction restrictions. Use that illustrative price to rehearse the same basket through the account journey:
| Stage | Expected result | What a failure points to |
|---|---|---|
| Browse anonymously, then use guest checkout. | Clear consumer prices including the applicable VAT. With the illustrative 19% rate, the product is EUR 119. | Different Visitor and Guest settings, or a theme that ignores the group. |
| Apply for trade access while approval is pending. | The account retains the intended public terms until approval. | Registration or another module assigning trade access too early. |
| Approve a domestic trade account and sign in. | The product shows EUR 100 excl. VAT; the payable product amount remains EUR 119 where that tax applies. | Wrong default group if display stays gross, or unintended exemption if VAT disappears. |
| Change the address, then log out and revisit. | Tax follows the agreed supply policy; logging out restores the public display without another buyer's prices. | Address-dependent exemption logic, session handling or an unsuitable shared cache. |
Use manual approval or a suitable account workflow to control default-group assignment. If you need an application queue, B2B Account Approval, Trade Account makes the configured trade group the default on approval. Decide who approves, which company details they check and what happens if access is withdrawn.
Automatic EU VAT Checker can optionally add group membership, but it does not change id_default_group. Its membership option is separate from native net display and is disabled by default; use the linked help page for configuration. Its tax policy uses the active billing address, so test it alongside the core address basis and the actual dispatch and delivery facts. A successful check against a foreign billing address must not by itself justify exempting goods delivered domestically.
For mixed anonymous traffic, consider clearly labelled dual prices, such as EUR 100 excl. VAT and EUR 119 incl. VAT, or Tax Display Switcher for a shopper-controlled view across prices, discounts, delivery and totals. Keep the consumer total clear wherever consumer rules apply. A preference toggle is not proof that a visitor is a business or qualifies for exemption. Check custom themes and full-page caches for prices leaking between audiences.
Qualifying business transactions
For an exempt intra-Community goods supply, check the customer VAT identification, qualifying movement between Member States, transport records and reporting conditions. A valid VIES result alone is insufficient. The supplier's exempt supply and the buyer's acquisition accounting are distinct. B2B services can instead fall under service place-of-supply and reverse-charge rules; domestic sales and special cases need their own treatment. See EU cross-border VAT guidance.
Review any legacy VATNUMBER_MANAGEMENT configuration too. Core contains number- and country-dependent VAT logic; it does not make a number a successful VIES check or prove the transaction's legal eligibility. Test validation outages, invalid numbers, changed addresses and invoice wording with your exemption policy.
Check VAT labels, shipping disclosure and unit prices
Open International > Locations > Countries to review the country's Display tax label option. Check theme translations for the tax-included and tax-excluded labels. Generic product labels are translated strings; renaming a Tax object does not replace them. Use a child-theme change only when the required wording or placement is missing.
For Germany, PAngV section 6 requires an indication that prices include VAT and other price components, and whether delivery or other charges apply. State the additional amount where it can reasonably be calculated in advance. “inkl. MwSt.” is a common formulation, not the only permitted literal text. A visible shipping-cost link can support the disclosure, but check the complete offer and checkout.
Unit prices help customers compare quantities. EU rules generally require them for relevant goods sold by weight, volume, length or area, with national and product-specific exceptions. For example, a 500 ml bottle priced at EUR 8.99 has a per-litre price of EUR 17.98. Check the required unit and exemptions for each market, including cases where selling and unit prices are identical.
- Open the product's Pricing tab and enter the actual price-per-unit amount and the separate unit label.
- For that bottle, enter the corresponding per-litre amount with the correct tax basis. A label such as “litre” alone does not tell PrestaShop that the package contains 500 ml.
- Save and check both net and gross output, combinations, specific prices and discounts. Include listing cards and mobile views, not only the product page.
- For bulk import, use the supported
unityandunit_pricefields under Advanced Parameters > Import. Do not assume an internal ratio is an available CSV mapping.
PrestaShop 1.7.8 stores the price-to-unit-price relationship in unit_price_ratio. In PrestaShop 9, the stored unit_price amount is the reference; the database ratio remains for compatibility. Edit the unit-price amount and unit label through the product form or supported importer, and let core maintain the ratio. Verify your theme actually renders the unit price in the required places. If combinations contain different quantities, check each pack size against its actual contents. A product import or supplier change that alters pack quantity needs a unit-price review even when the selling price stays the same.
Build tax rules around product tax categories
PrestaShop uses three objects: a Tax is a named rate, a Tax Rule matches a country and optionally a state or postcode, and a Tax Rules Group bundles rules for assignment to products and other taxable charges.
- Under International > Taxes, create or verify the current rates you actually need. Check localisation-pack rates before using them.
- Under the Tax Rules tab, create a group for a product tax profile, such as standard-rated goods or qualifying books.
- Add destination rules within that group for the countries and regions you serve. The same product can have different qualifying rates in different destinations.
- Assign the group to each product's Pricing settings in the correct shop context. Core does not automatically inherit a tax group from a catalogue category.
- Review Based on, backed by
PS_TAX_ADDRESS_TYPE. For ordinary destination-based goods sales, use the delivery address and test when billing and delivery differ. - Place a test order for every relevant destination and tax category. Check the product, carrier, discounts and invoice.
A missing matching rule can leave a product untaxed without an obvious checkout error. Check the group's active state, product assignment, address, state and postcode, exemption integrations and global tax settings. A zero result can be intentional; it is a review candidate, not automatic proof of a defect.
This query finds active products with no group in shop 1 and language 1. Adjust those IDs and the table prefix:
SELECT p.id_product, pl.name, p.reference, ps.id_tax_rules_group
FROM ps_product p
JOIN ps_product_shop ps ON ps.id_product = p.id_product
JOIN ps_product_lang pl
ON pl.id_product = p.id_product
AND pl.id_shop = ps.id_shop AND pl.id_lang = 1
WHERE ps.id_shop = 1 AND ps.active = 1
AND ps.id_tax_rules_group = 0
ORDER BY p.id_product;
When a rate changes, update or replace the relevant rate and rule mappings deliberately, then test new orders. Disabling a Tax removes it from active selection lists but does not reliably stop an existing rule from using it. Core historizes used taxes when updating them; preserve historical invoices and order tax data rather than recalculating old documents from today's rules.
In multistore, verify tax-group associations and each product's shop-specific assignment. Check the default country and other configuration in each shop context. Sharing a definition does not guarantee that every shop uses it correctly.
Rehearse a tax change before switching
- Write the expected result for each product tax profile and destination, including intended exemptions. Keep the current product assignments, rules, carrier settings, address basis and rounding settings with the change record.
- On staging, configure the agreed changes and test a domestic consumer, an overseas consumer and a business buyer. Include a mixed-rate basket, repeated quantities, a discount and taxable extras where offered.
- Change only the billing address, then only the delivery address. Record which change should affect product and delivery VAT, and compare the result with the exemption module's policy.
- Try an invalid VAT number, a valid number that does not qualify the supply and the validation-unavailable path using a supported test mechanism. Confirm the customer message, tax charged and evidence retained for the decision.
- Read the resulting invoice and process a partial refund through the normal workflow. Compare checkout, payment, order, credit document and the integration's export against the expected figures.
- Check a new product and a sample imported product in each affected shop. Add tax-group verification to the product-creation and import checklist so later catalogue work does not undo the setup.
For an unexpected untaxed line, trace the product assignment to the rule matching that exact address before changing a rate. If the tax amount is right but the label is wrong, investigate translations and theme output instead of editing the tax calculation.
Test rounding, shipping and other charges
Under Shop Parameters > General, distinguish Round mode from Round type. The mode controls how a value rounds; the type controls the calculation level:
- Each item: round the unit amount before multiplying by quantity.
- Each line: multiply for a product line, then round that line.
- Total: accumulate the relevant amounts before final rounding.
A single product line with quantity greater than one can expose a difference. Test quantities, mixed rates, discounts and currency conversion against the accounting method you need. Do not infer a nationwide rounding mandate from a generic country comparison.
Each carrier has a tax rules group in Shipping > Carriers. Set it according to the applicable treatment, including mixed-rate carts. Gift wrapping has its own tax group under Order Settings. If ecotax applies, configure its tax settings and product amounts separately. A blanket “No tax” or one standard shipping rate is not suitable for every transaction.
Reconcile the product, shipping, gift-wrapping and tax totals between checkout, payment, admin order and invoice. Test refunds and credit documents too. See accounting and invoices for the document workflow.
Apply the distance-sales threshold and choose OSS reporting
The EUR 10,000 threshold is VAT-exclusive combined qualifying intra-Community distance sales of goods and cross-border telecommunications, broadcasting and electronically supplied services. It applies only when the supplier is established in one Member State, with the qualifying goods dispatched from that State, and the total does not exceed EUR 10,000 in both the current and preceding calendar years. It does not cover every service or imports.
For example, EUR 4,000 to France, EUR 4,000 to the Netherlands and EUR 3,000 to Spain totals EUR 11,000. The threshold is combined, not per destination. When it is exceeded, destination taxation applies from the transaction that exceeds it. Eligible sellers may choose destination treatment below the threshold; that choice binds for at least two calendar years. See the Commission's threshold guidance.
OSS is optional reporting, not the rule that creates the destination tax liability. The Union scheme covers eligible intra-Community distance sales and certain consumer services, with special provisions for deemed suppliers. The non-Union scheme covers eligible services supplied by businesses not established in the EU. Service coverage is broader than TBE alone. Domestic VAT returns and other obligations can still apply.
For Union and non-Union OSS, registration normally starts on the next calendar quarter. A first-supply exception can allow commencement on the first eligible supply if you notify the identification State by the tenth day of the following month. Missed timing can require direct registration and accounting in the relevant consumption States. Check the registration rules before collecting the first affected payment.
Since 1 January 2025, eligible EU-established small businesses can also seek the optional cross-border SME exemption. It has a EUR 100,000 Union turnover ceiling, national thresholds and further conditions. It is a separate exemption scheme, not an automatic consequence of being below the distance-sales threshold. Review the SME scheme conditions with your adviser.
Give someone responsibility for monitoring the qualifying total across the relevant business's sales channels, not just this storefront. Agree how you will identify the threshold-crossing transaction and make the configuration effective at the right time. Creating destination rules does not register you for OSS, and registration alone does not update the shop's rules.
Handle low-value imports separately
IOSS is optional for eligible distance sales of imported goods in consignments with an intrinsic value not exceeding EUR 150, excluding excise goods. It collects destination VAT at sale and uses a monthly return. An intermediary may be required, particularly for suppliers outside the EU, subject to the applicable exceptions. See Irish Revenue's IOSS guidance.
Assess intrinsic value and consignment rules before offering IOSS. Artificially splitting one transaction above EUR 150 does not make it eligible. Agree the secure transmission of the IOSS identifier with the carrier or customs representative. Do not expose that identifier publicly.
IOSS handles VAT; it does not guarantee that a delivery has no customs charge or carrier fee. From 1 July 2026, the old low-value customs-duty exemption ended and a temporary EUR 3 duty applies to relevant low-value imports under transitional rules. Check how it is calculated and paid for your goods and shipping arrangement in the Commission customs guidance. Do not advertise “no doorstep charges” without confirming the complete delivery terms.
Prepare records and returns from classified transactions
Union and non-Union OSS periods are quarterly; IOSS periods are monthly. Return and payment are due by the end of the following month. Quarterly due dates are 30 April, 31 July, 31 October and 31 January. Nil returns can still be required. See the OSS filing guidance.
Keep OSS and IOSS records for ten years from the end of the transaction year and make them electronically available when requested. Destination authorities retain audit and enforcement powers. OSS centralises filing for covered supplies; it does not remove every local tax obligation. The record-keeping rules specify the information and access requirements.
Record the transaction type, dispatch and destination, tax point, taxable amount per rate, VAT, currency and conversion, payments, returns and corrections. For goods, keep dispatch and transport information. TBE services have their own customer-location presumptions, exceptions and supporting data rules. Do not turn a TBE rule about two nonconflicting location items into a universal requirement that physical-goods billing and shipping addresses must match.
PrestaShop stores order addresses, carrier identifiers, currency and conversion rate. A checkout IP is not a native persisted orders field. If your process needs IP data, identify a separate lawful collection and retention mechanism; connection or session data is not a guaranteed long-term order archive.
Core order exports are inputs to a reporting process, not a finished OSS or IOSS return. A query that excludes only your home country also includes possible exports, B2B sales and other out-of-scope supplies. Adding order totals can mix currencies and miss multiple rates, tax points, refunds and corrections.
- Classify each supply and identify its applicable reporting scheme.
- Exclude B2B and other out-of-scope transactions from the B2C OSS population.
- Use dispatch country and EU VAT-territory destination, rather than a simple non-domestic country filter.
- Calculate taxable events and corrections per rate in the required reporting currency.
- Reconcile to invoices, credit documents, payments and the general ledger before filing.
VIES records can support B2B classification and exclusion from OSS. They are not the foundation of a consumer OSS return. Build retention and access controls before database cleanup or customer deletion can erase required tax records.
Agree the reporting handover before quarter-end
Give your accountant a sample containing a domestic sale, a qualifying cross-border consumer sale, a business exemption and a refund. Ask which rows belong in each return and what source evidence supports the classification. An invoice issue date, payment date and tax point can differ; specify the selection basis instead of choosing whichever date the exporter offers first.
| Part of the specification | Acceptance check |
|---|---|
| Population and shop scope | Each row identifies the selling entity, shop, dispatch and destination, supply type and scheme decision. |
| Tax detail | A mixed-rate order retains the taxable amounts and VAT for each rate, including relevant delivery and other charges. |
| Corrections | A partial refund links to the original transaction and reaches the agreed reporting period without subtracting the whole order. |
| Currency and traceability | Original amounts, conversion method and reporting amounts can be traced back to invoices, credit documents and payments. |
Orders CSV List Exporter supplies saved order, product or invoice layouts; Invoice CSV List Exporter selects invoice and credit slip lists by document issue date. Financial Revolution brings orders, refunds and operating costs into financial reports with a chosen reporting currency. Check their actual fields against the agreed specification: none of those descriptions establishes a ready-to-file OSS or IOSS return.
Connect language, currency and destination handling
Enable and translate the markets you can support. When you direct sales at consumers in another country, check that market's mandatory consumer price disclosures separately from the VAT calculation: a delivery-country tax rule does not settle which consumer protection rules apply. Review products, variants, slugs, checkout, delivery terms, VAT labels, exemption notices, emails and invoices. Use the available languages and currencies screens under International. Test the active theme's selectors and the selected values through payment and order confirmation.
Review exchange-rate updates and currency-specific prices. A clean converted display must still preserve the correct payable amount and tax rounding. Country-targeted specific prices can set market prices; customer groups are not automatically tied to countries.
Use hreflang to help search engines associate alternate language or regional pages. It is a recommended signal, not a guarantee that the right version appears or a prerequisite for Google to discover translations. Separate domains, catalogues or legal entities may call for multistore rather than translations alone.
Choose shipping zones from actual tariffs, parcel sizes, delivery times and return arrangements. Select payment methods from your customers' needs and provider availability. The UK, Switzerland and Norway need their own tax and customs analysis; do not treat geographic Europe as a single VAT territory.
- Choose the initial destination markets and establish their tax treatment and registration timing. Record where stock is held and dispatched: moving fulfilment to a warehouse in another country can change the analysis.
- Configure product and carrier tax rules before accepting affected orders.
- Complete translations, currency and payment configuration.
- Test an order from each market, including differing billing and delivery addresses.
- Check invoice, refund and reporting output before expansion.
See international setup and EU compliance for the connected work.
What to ask your developer or agency
- Which existing modules, overrides, theme templates, caches and integrations can alter the price, tax or exported figures, and which will remain responsible after the change?
- Where are the accountant-approved expected results and the matching test orders, invoices and corrections for each affected market?
- Does changing the customer's default group also change discounts or access, and can revoking approval restore the intended retail journey?
- What settings and product assignments will change at cutover, who checks existing carts, and who can restore the previous configuration if a new order is wrong?
- How will staff correct orders already placed under a wrong setup, preserve issued documents and communicate with the accountant rather than rewriting history?
Use an agreed change window after the rehearsal passes. Pause conflicting imports and price synchronisation while applying the configuration, clear affected caches and repeat the relevant purchases. Restoring settings does not undo orders or documents created during the change, so retain their references for review.
If an existing module has already been chosen, the PrestaShop Module Installation & Configuration Service can install it, configure the agreed settings and verify the affected journey within its written scope.
Present prices and reductions honestly
For covered EU price-reduction announcements, establish the applicable prior price from your history before configuring the offer. The general reference is the lowest price applied in at least the preceding 30 days, subject to national rules and exceptions. Regular catalogue price, recommended retail price and legally required prior price are different concepts.
If a product normally costs EUR 50, was offered at EUR 40 two weeks ago and now costs EUR 35, the relevant 30-day comparison can be EUR 40 to EUR 35, or 12.5%, rather than a claimed 30% reduction from EUR 50. Check the rule for the actual campaign, audience and market. Germany's PAngV section 11 includes national provisions for progressive reductions and specific exceptions.
Specific prices and catalogue price rules do not by themselves establish the required historical reference. Check whether your theme strikes through the regular catalogue price, which can differ from the lowest eligible price in the required period. Verify the strikethrough, percentage, banner and email together. Do not alter your catalogue base price merely to invent an anchor. Agree the applicable prior-price and disclosure rules with an adviser experienced in consumer pricing law for your target markets. Keep a price-history process, or use Omnibus Price Compliance to record public prices and show supported prior-price references; follow its help page for setup. Installation supplies no past history. The module hides references without enough evidence and hides cart references when a cart rule applies, so verify the actual campaign and display location rather than assuming installation makes every comparison ready.
Use price endings and offer tiers as tests
Compare EUR 49.99, EUR 50.00 or a calculated EUR 47.83 when you have a clear business reason. Treat perceived value, premium positioning and precise pricing as hypotheses for your audience. Do not assign a preferred ending to an entire nationality or promise a conversion effect.
Set exact product prices or use specific prices with suitable country, currency, group, quantity and date conditions. Catalogue price rules apply fixed or percentage reductions across matching products; they do not generally turn every price into a .99 or .95 ending. That requires calculating the target per product or using a tested rounding feature.
You can compare transparent tiers such as Basic EUR 29 for one item, Standard EUR 49 for two and Premium EUR 55 for three. Use Packs for distinct bundles or quantity-specific prices for volume tiers. Show accurate contents and any genuine saving against separately available items. Label recommended-price comparisons distinctly from your own prior-price reduction.
Keep the currency and payable amount clear. Test typography, colour and price placement for readability rather than assuming a universal psychological response. Reducing currency precision is not selective removal of trailing zeros: it can change the display of real cents across cart, checkout and invoices. If you only want EUR 49.00 to appear as EUR 49, use a carefully tested display change that still preserves EUR 49.50.
Choose a price change you can reverse
Distinguish a permanent base-price change from a temporary promotion before you choose the tool. For bulk repricing, Mass Price Updater provides a preview and records previous values for restoration. For timed offers, native dated specific prices may be sufficient; Smart Dynamic & Scheduled Discounts adds scheduled campaigns and price or margin limits. Check existing rules and imports before introducing another price writer.
- Save the affected products, combinations, shop scope, currencies and current prices. Include wholesale prices and active specific prices in the review where relevant.
- Preview the resulting net and gross prices, unit prices and the applicable prior-price comparison. Check the margin after tax, discounts and delivery costs against your own cost data.
- Test an ordinary purchase and overlapping quantity, group or voucher conditions. Confirm which rule wins and what happens when a scheduled offer expires.
- Keep the restoration record and the campaign dates. Undoing the current selling price does not erase the price history or remove the need to correct a misleading announcement.
Use real campaign deadlines and stock information. Do not reset a countdown on each visit or invent sales activity. Plan an experiment around one change, suitable sample size and calendar coverage. Measure margin and revenue per visitor as well as conversion. Customer groups can hold assigned price variants, but native groups do not randomly split anonymous visitors into an A/B test. Check the applicable reduction rules for the experiment itself.
Questions owners ask
Do I need a module just to give approved trade buyers net prices?
No. Use the native default-group setup above. Add a module when you need a missing workflow such as applications, visitor choice or validation, and test its interaction with the settings you already use.
Can I keep the same gross price when the destination rate changes?
You need a pricing policy as well as a tax rule. With an unchanged net base, a different rate changes the gross total. If you want a fixed market-facing gross price, calculate the corresponding net price, configure the appropriate specific price and check the margin.
Why does the price change after the customer enters an address?
Compare the browsing location and tax context with the address used at checkout. An intended destination recalculation can explain it; a missing rule or exemption can also cause it. Trace that basket before trying to force the displayed figure.
Will enabling OSS or a VAT-number module prepare my return?
No. Registration, checkout tax and reporting remain separate jobs. Use the reporting handover above to agree what your accountant receives, including exclusions, refunds and conversion, before relying on an export.
Should I change old invoices after correcting a tax setting?
Preserve the original documents and ask your accountant which correction workflow applies to affected transactions. Changing today's rules does not repair earlier records, and recalculating them can destroy the evidence of what happened.
Can I launch the promotion as soon as price-history recording starts?
Recording starts with the data available; it cannot supply missing earlier public prices. Use a comparison only when you have the required evidence for that offer and market. Review the full announcement if the reference is unavailable.