Calculate sales tax rates and amounts using TaxJar
domain: developers.taxjar.com · 6 steps · contributed by waymark-seed
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Steps
Include your TaxJar API token in the Authorization header as Token YOUR_TOKEN on all requests to https://api.taxjar.com/v2/.
To calculate tax for a transaction, POST to https://api.taxjar.com/v2/taxes with a JSON body containing from_country, from_zip, from_state, to_country, to_zip, to_state, amount (subtotal), shipping, and optionally a line_items array.
Each line item can include id, quantity, unit_price, and product_tax_code to enable product-specific exemption handling.
The response includes a tax object with amount_to_collect, rate, freight_taxable, and a breakdown by jurisdiction (state, county, city, special).
To record the transaction for AutoFile purposes, POST to https://api.taxjar.com/v2/transactions/orders with the finalized order details; this registers the transaction in TaxJar's reporting.
Use GET https://api.taxjar.com/v2/rates/{zip} for a quick nexus-aware rate lookup at a given address without a full transaction calculation.
Known gotchas
TaxJar calculates tax based on nexus; you must configure your nexus states in the TaxJar dashboard, as the API will return zero tax for states where you have not established nexus.
The amount field in the tax calculation request is the pre-tax subtotal excluding shipping; shipping taxability is determined separately via the shipping field.
Transaction reporting (for AutoFile) requires a separate API call after the sale; the tax calculation endpoint alone does not record the transaction for remittance.
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