Back taxes are taxes that weren’t paid at the time they were due, typically from a prior year. You can owe back taxes at the federal, state, or local level, and you can owe them for a number of reasons.

Many people owe back taxes because they didn’t have enough money withheld for taxes from their paychecks throughout the year. Some people may also owe because they were unaware that unemployment benefits are taxable most years, and they didn’t have money automatically withheld. Selling stock or other investments at a profit could result in capital gains taxes, which you must report. You could also wind up owing back taxes because you made a math error or deliberately underreported your income.

A government might implement different approaches to collect back taxes, including criminal charges, offering a voluntary disclosure program that allows a broad variety of payment methods, or tax liens.

If the taxes remain unpaid, the tax authority could use a tax levy to legally seize the taxpayer’s assets (such as bank accounts, investment accounts, automobiles, and real estate) to collect the money it is owed.