You Can’t File Your Taxes Online Without This Number. Here’s How to Find It

THE best tax software has become so good at navigating the complex federal income tax rules that most filers can complete and submit their tax returns to the IRS without having to think about complicated worksheets for tax credits and deductions.

However, there is one tax term that you will need to understand for yourself in order to file your tax return online: adjusted gross income Or AGI.

You’ll need your AGI from last year’s taxes to verify your identity online when you file in 2026, but this year’s AGI is also important. This will impact the tax deductions and tax credits you can claim, as well as your tax bracket and tax rate.

Learn everything you need to know about AGI, how to find last year’s information, and what to do if you can’t locate it. For more tax tips, find out when your taxes are due and how to track your tax refund.

What is adjusted gross income, or AGI?

Adjusted gross income includes all the money you earned in a year minus certain adjustments. These adjustments are also called “non-standard deductions,” meaning you can use them to reduce your taxable income even if you take the standard deduction and don’t itemize. AGI will also sometimes be referred to as “taxable income.”

Some of the above-the-line deductions that reduce your AGI include:

• Retirement account contributions
• Student loan interest
• Health savings account contributions
• Child Support Payments
• Educator fees
• Qualified education expenses
• Moving costs for military personnel
• Certain expenses for eligible artists
• Half the self-employment tax

Why do I need my AGI from last year to file my taxes online in 2026?

The IRS uses your AGI from the previous year to verify your identity when you file your taxes electronically. You can also use last year’s five-digit self-selection PIN, if you created one.

How can I find my AGI from last year?

The easiest way to find out last year’s AGI is to look at your 2024 tax return, specifically Line 11 of Form 1040. If you used online tax software to file last year, you can log in to your account and view your 2024 tax return.

If you don’t have last year’s return and can’t access it online, you can also find your AGI from your 2024 taxes with a IRS account online. Once logged into your IRS account, you can get a transcript of last year’s taxes that shows your AGI.

If you don’t want to create an IRS account, you can also use Form 4506-T to request a 2024 tax transcript by mail.

What should I use for last year’s AGI if I didn’t file a return?

If you didn’t file a tax return in 2025 or are a first-time filer in 2026, just say $0 for your AGI.

If you file your income taxes jointly and your partner didn’t file a return last year, enter $0 for the person who didn’t file a return. Most online tax software will simply ask if you have filed a return and will automatically enter $0 if you have not.

What is MAGI, or modified adjusted gross income?

Your modified adjusted gross income, or MAGI, is another important number that can potentially impact your tax refund. Your MAGI is determined by adding certain deductions used to calculate AGI.

The most common deductions included in the MAGI calculation are:

• Student loan interest
• Tax-free social security benefits
• Tax-exempt interest
• Income earned abroad
• Half the self-employment tax

For most taxpayers, AGI and MAGI will be very similar, but one difference can be critical because some credits and deductions use thresholds based on MAGI. Your MAGI will determine if you are eligible for a Roth IRA and whether your pension contributions are deductible.

Several tax credits also use MAGI to determine eligibility or phase-out, including the Child Tax Credit, Education Credits, and the Premium Tax Credit for Assistance to Public Marketplace Health Insurance Plans.

For more tax advice, find out what to do if you have not received your W-2 form this year and how new crypto reporting rules work.