Form 8606 is a tax form used to report certain types of activity in Individual Retirement Accounts (IRAs), especially when you’ve made after-tax contributions or taken distributions that include those contributions. If you add money to a traditional IRA that you didn’t deduct on your taxes, or if you convert a traditional IRA to a Roth IRA, this form helps the IRS track which part of your IRA hasn’t been taxed. It also prevents you from paying taxes twice on the same money. You only need to file it when specific actions apply, but when you do, it plays an important role in making sure your taxes are calculated correctly.