Something like ten years ago now, Washington State changed their sales tax requirements in a way that required the seller to look up the four-digit rate code of the buyer, both for determining the rate to charge and later for remitting to the state. The quarterly file they provide with this information is ~150000 rows. Prior to that date, you just reported for the jurisdiction in which the business was registered.

Between this and similarly far-reaching laws (e.g., GDPR), it's becoming increasingly burdensome for small players to the point where secondary services like Avalara are effectively required.