Fetch sales tax rates for a specific address using the TaxJar Rates API and apply product-level tax codes

Steps

1. Authenticate to the TaxJar API by including your TaxJar API token in the Authorization header as a Bearer token on all requests
2. Call GET /v2/rates/{zip} with optional query parameters for street, city, and state to retrieve the combined sales tax rate for the destination address; inspect the combined_rate, state_rate, county_rate, and city_rate fields in the response
3. Note that the Rates endpoint returns general rates and does not account for product-specific exemptions or reduced rates; for accurate product-level tax, use the TaxJar Tax endpoint (POST /v2/taxes) instead
4. When calling POST /v2/taxes, include line_items with product_tax_code values from TaxJar's published tax code taxonomy; TaxJar uses these codes to apply category-specific rates and exemptions such as reduced rates for groceries or clothing
5. Include the from address (nexus location) and to address (ship-to) in the request; TaxJar uses both to determine whether nexus exists and which jurisdiction's rules apply
6. Validate the tax_source field in the response to confirm whether the calculation is destination-based or origin-based, as this affects which rate is applied for in-state transactions