The Adjusted Gross Income (AGI) is the amount at the bottom of the first page of your tax return. So, if you file your own tax return, print a copy or save it to your computer before you log out. If you use a tax preparation service, make sure you get a printed or emailed copy from them when the tax return is filed. Trying to track down the person that prepared your taxes six months or more later to get a copy can be a frustrating process.
There are also many other reasons to always maintain a copy of your tax returns. For example, you may be asked to provide a copy of your tax return for your child when they apply for college and/or financial aid. If you are considering filing bankruptcy, you will need to provide a copy of your last two years of tax returns to the Trustee. Whenever you wish to buy a home, you will be asked to provide copies of tax returns by whomever you are applying with for a mortgage loan.