Tax on a B2B order is rarely a flat rate. It depends on where the goods ship, what they are, whether the buyer holds a valid exemption certificate, and in the United States whether you have nexus in that state at all. Keeping those rules current by hand across thousands of jurisdictions is not realistic, so most sellers hand the calculation to a service.
Avalara is the most common of those services, and it can be connected at more than one point. The ERP can call it when the invoice is produced, the commerce platform can call it at checkout, or both can. Deciding which system owns the call matters more than it sounds. If the storefront quotes one tax figure and the ERP invoices a different one, somebody in finance reconciles the gap by hand for as long as the mismatch lives.
Alternatives exist, including Vertex and the tax engines built into Acumatica and the commerce platforms themselves. The choice usually comes down to how many jurisdictions you sell into and whether exemption certificates are already managed in Avalara.
Why it decides a platform
If tax is calculated in two places, the storefront total and the ERP invoice will eventually disagree. Naming one system as the owner of the calculation, and having the other read the result, removes a whole class of customer service work.
Also called: AvaTax, Avalara AvaTax, tax automation, sales tax engine.
Last updated 2026-08-20.