If your business sells products online, has employees working remotely in other states, or ships goods through a fulfillment network, you may already owe taxes in states where you’ve never set foot—and most business owners don’t find out until someone comes looking. The rule that makes that possible is called nexus, and the threshold that triggers it could be lower than most people expect.

Most homeowners tuck renovation receipts into a drawer and never think about them again. But those records can determine how much of your home sale profit is taxable years, or even decades, down the road. Here’s what you need to know before it’s too late to do anything about it.