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What the tax provider endpoint does
Shopware hands your endpoint the full cart — line items, customer, addresses — and you return the tax per position and the totals. Shopware then displays and stores exactly what you returned. One system decides tax, and everything downstream agrees with it.
When you actually need it
Selling into several EU countries, handling reverse charge, or dealing with reduced rates that depend on the product and the destination. A hard-coded 19% and a rule table will get you through year one and fail an audit in year three.
Latency is now a checkout risk
Every cart recalculation may call your endpoint. Cache aggressively on identical carts, set a hard timeout, and decide in advance what happens when the tax service is down — because it will be, on the busiest day.
Store the answer, not just the number
Keep the full response with the order: rates, jurisdictions, the reason for reverse charge. When a tax auditor asks why order 4711 had 0% VAT two years ago, that stored payload is your entire defence.
- One system owns tax; the shop displays it.
- Cache and time-out the tax call, or checkout dies with it.
- Archive the full tax response with the order.
Frequently asked questions
Yes — Shopware can hand your endpoint the full cart, line items, customer and addresses, and take back the tax per position plus the totals. What you return is what the shop displays and stores. The value is not the arithmetic; it is that one system decides tax and everything downstream agrees with it instead of quietly disagreeing.
If you sell one product category into one country, the rule table is enough and a tax provider is overkill. It earns its keep when you sell across several EU countries, handle reverse charge, or have reduced rates that depend on both the product and the destination. A hard-coded rate gets you through year one comfortably and fails an audit in year three.
Whatever you decided in advance — so decide in advance. Every cart recalculation may call that endpoint, which means you have put an external service into the checkout path. Cache aggressively on identical carts, set a hard timeout, and write down what the shop does when the call fails. It will fail, and it will pick your busiest day to do it.
The full response, not just the number that ended up on the invoice. Rates, jurisdictions, the reason a position was reverse charge — store the whole payload with the order. When someone asks in two years why order 4711 carried no VAT, that archived response is your entire defence. The figure on its own tells you what happened and never why.
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