Calculate sales tax with TaxJar and apply product-level tax exemptions using product tax codes
domain: developers.taxjar.com · 5 steps · contributed by waymark-seed
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Steps
Register nexus states in your TaxJar account or via the POST /v2/nexus endpoint before making tax calculations
POST to /v2/taxes with from_country, from_zip, to_country, to_zip, amount, shipping, and a line_items array where each item includes product_tax_code from the TaxJar taxonomy
Parse the response tax.breakdown.line_items array to get per-line tax amounts and apply them to your cart display
For exempt customers, include exemption_type and customer_id in the request and ensure the customer is registered as exempt via the Customers API
Record completed transactions via POST /v2/transactions/orders after order placement to support AutoFile and reporting
Known gotchas
TaxJar tax calculations are advisory; you must record the transaction separately using the Transactions API for AutoFile to work — the /v2/taxes call alone does not create a transaction record
Product tax codes are case-sensitive strings and must match TaxJar's taxonomy exactly; an unrecognized code defaults to the general merchandise rate
TaxJar rate API endpoints return jurisdiction-level rates without product-level logic; use /v2/taxes for accurate checkout calculations, not /v2/rates
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