A woman in Ohio loves your candles. A guy in Texas keeps coming back for your supplements. A dozen orders a day becomes a hundred. Revenue crosses $500k, then $1M. You’re reinvesting everything, hiring, running your first real ad campaign.  Tax season? Your accountant handles income taxes in April. You assume it’s handled. But here’s what’s actually happening in the background. Before 2018, online sellers collected sales tax only in states where they had a physical presence, such as a warehouse, an office, or an employee. Then, the Supreme Court ruled in South Dakota v. Wayfair , and that changed for good. States can now require you to collect sales tax based on how much you sell there, no physical presence needed. It’s called economic nexus . The most common trigger: $100,000 in sales or 200 transactions in a state within a 12-month period. Some states set the bar lower. Cross that threshold, and you’re legally required to register in that state, collect the correct rate, and file returns on schedule.…