Usually I'd use a combination of my Mint records (which had convenient totals for each online merchant, of which I really only used 5 or 6 in a typical year) an

Usually I'd use a combination of my Mint records (which had convenient totals for each online merchant, of which I really only used 5 or 6 in a typical year) and the Massachusetts safe harbor law (which essentially allowed me to assume that I spent 1% of my AGI on untaxed purchases less than $1000, and pay use tax based on that number). If I bought anything online or out-of-state that cost more than $1000, I'd add that in separately, but that happened rarely enough that it was pretty hard to forget how much I spent on those items. What we have right now is a situation where some stores collect taxes in some states. As a consumer, I would prefer it if all stores collected taxes for all states, for three reasons. First, I wouldn't have to figure out which stores already collected taxes, so it would save me time. Second, because I like seeing how much I'm going to pay for something, taxes included, at the time of purchase. And third, because I believe that taxes should be levied fairly and consistently, and that would put online stores on the same footing as brick-and-mortar stores, and honest taxpayers on the same footing as people who are inclined to see what they can get away with. As a startup founder, however, I'm less enthusiastic. The process of filing taxes in all 50 states would be a huge burden. If a national sales-tax clearinghouse existed, it would be a different story, but under the status quo, it's just too much paperwork for a small company to handle.