Understanding tax remittance starts with knowing where you have tax obligations and how much you need to collect.
All but five U.S. states have a statewide sales tax (the exceptions are Alaska, Delaware, Montana, New Hampshire, and Oregon). So do Puerto Rico and the District of Columbia.
(We should also note that while Alaska doesn’t have a statewide sales tax, it does allow local jurisdictions to establish their own sales taxes. And Montana has a provision that allows certain resort communities to levy a sales tax.)
So the first step in calculating the tax due on a transaction — and how much the merchant needs to collect from the customer — is determining what states they’re doing business in, then understanding whether there are also tax requirements from counties, cities, or other local jurisdictions.
If you were operating a brick-and-mortar store in the 20th century, that would be relatively easy. You’d know what state (or states) you had locations in, and since that’s where the transactions took place, that’s where you’d owe tax (aka physical nexus). There were complicating factors, of course — different products may be taxed at different rates by one jurisdiction. But for the most part, you just needed to figure out the combined state and local sales tax rates for each of your locations, and apply those rates to each transaction to ensure you were collecting the right amount.
But in 2018, the U.S. Supreme Court changed all that with its decision in South Dakota v. Wayfair, which overturned the physical presence requirement. The Wayfair decision allowed states to impose a sales tax obligation on sellers with no physical presence (aka economic nexus).
That made calculating sales tax much more challenging. There are more than 12,000 sales and use tax jurisdictions in the United States — some of them overlapping — and online merchants can have tax obligations in any number of them. (You can get a free sales tax risk assessment from Avalara that shows the states where your business may have tax obligations.)
Once you know the states where you have nexus, you need to understand where your customers are and what the tax rates are where they live. Given the complexity of achieving this, some merchants may be tempted to take shortcuts in calculating how much tax they need to collect from buyers. There are two problems with this:
If you don’t collect enough, you run the risk of having to make up the difference between what you’re obligated to remit to state and local jurisdictions and what you collected out of your cash reserves.
If you collect too much, you run the risk of alienating customers and losing sales to competitors who correctly calculate the exact amount they’re obligated to remit and only collect that amount from customers. You could also face legal action.
One more thing to consider: Depending on who your customer is or what they intend to do with the goods they’ve purchased from you, specific sales might be exempt from sales tax. But, you as the seller will need to have documentation — typically in the form of a tax exemption certificate — to validate and confirm why you didn’t collect sales tax on a specific transaction.