Recurly allows you to mark specific customer accounts as tax exempt, removing the account from any taxes. To mark an account as tax exempt, edit the Account Information on the account and select an Entity Use Code. Entity Use Code is an Avalara field. We suggest talking with your Avalara representative about which Entity Use Codes you should use.
We do not currently have a way for a customer to note that they are tax exempt at purchase. We recommend having a message at purchase that any tax exempt customers should contact you first. You will need to make an account for the customer and mark them with an Entity Use Code. The customer can then sign up with the same account email address. They will likely still see a tax preview, but will not be charged tax.
Avalara has a tool for managing exemption certificates called Avalara CertCapture. Recurly doesn't have an integration with Avalara CertCapture, but we are collecting requests for this functionality. If you would be interested in using Avalara CertCapture with Recurly, please submit a support ticket with this request at https://support.recurly.com/.