This documentation is for Taxamo v1. If your account is with Taxamo v2 use the documentation at integrate.taxamo.com/doc.
If you are uncertain of your version please contact support@taxamo.com for assistance.

How to set customer address and what fields are required (US)?

If you are using Taxamo Checkout the address details can be marked as required - please check the metadata options for Taxamo Checkout in our documentation.

See an example in our documentation of setting the invoice address when creating a transaction.

For the United States, address details are necessary for determining sales tax. If you have address verification enabled (i.e. USPS user id set on US Sales Tax settings page in Taxamo portal) the required fields are street, city, state, & zip code and the transaction cannot be created unless the address is verified. Address verification is important as a single zip code can cover multiple counties with different sales tax rates. If address verification is not enabled it is sufficient to provide zip code, city and state details, but in some cases that can result in the incorrect tax being returned. Also remember that you can configure which states that you wish to collect taxes from, under your TaxCloud account -> Tax states.