Batch US Sales Tax Rate Lookup (Streamlined Sales Tax)

Use this endpoint when you need sales tax rates for multiple US locations in a single round-trip — ideal for e-commerce checkout pipelines, batch invoice generation, or compliance audits covering up to 100 addresses at once. It is specifically optimized for Streamlined Sales Tax states. For a single location lookup, prefer the sibling single-address endpoint. For monitoring tax rate changes over time, use the quarterly changes feed endpoint.

• Invalid ZIP code format returns a validation error for that location
• Sale date outside of allowed range (before previous quarter start) returns an error
• Non-SST state ZIP codes may return no results or an unsupported-state error
• Submitting more than 100 locations returns a 400 bad request
• Missing required 'zip' field for any location item causes a validation failure
• Payment failure via x402 protocol results in a 402 Payment Required response