You can file two years of taxes together, but not on one form: the IRS needs a separate Form 1040 for each tax year, prepared on that year’s version of the return, and you send them in at the same time. Tax brackets, the standard deduction, and available credits change every year, so 2023 income belongs on a 2023 return and 2024 income belongs on a 2024 return. Nothing stops you from finishing both and submitting them the same day. If you owed tax in either year, penalties and interest have been running since that year’s original due date, and filing now is what stops the largest of those penalties from growing further.
Why Each Year Needs Its Own Return
The IRS cannot process a return that mixes income from different periods because the rules themselves are different from year to year. A 2023 return must use the 2023 Form 1040 with 2023 brackets and deduction amounts; a 2024 return must use the 2024 version. Using the wrong year’s form will cause the IRS to reject the filing. Prior-year forms and instructions are available through the IRS Prior Year Forms and Instructions search tool, which goes back decades.1Internal Revenue Service. Prior Year Forms and Instructions
Use the filing status you qualified for during each specific tax year, not your current one. If you were single in 2023 and married in 2024, the 2023 return is filed as single and the 2024 return as married filing jointly or separately. Income, deductions, and credits on each return follow the rules in effect during that tax year, which the matching year’s instructions lay out.
What Filing Late Will Cost You
Two separate penalties run at the same time on a late return where you owed tax, and interest compounds on top of both.
Failure-to-File Penalty
For every month or partial month a return is late, the IRS charges 5 percent of the unpaid tax, capping at 25 percent after five months.2Internal Revenue Service. Failure to File Penalty Once a return is more than 60 days overdue, a minimum penalty kicks in. For tax year 2026 returns, that minimum is $525 or 100 percent of the unpaid tax, whichever is less. If you expect to owe nothing, this minimum doesn’t apply, but any actual balance triggers it fast.
Failure-to-Pay Penalty
A separate 0.5 percent monthly penalty runs on any unpaid balance from the original due date, also capping at 25 percent.3Internal Revenue Service. Failure to Pay Penalty When both penalties apply in the same month, the failure-to-file penalty is reduced by the failure-to-pay amount, so the combined monthly hit is 5 percent rather than 5.5. After the filing penalty maxes out at five months, the payment penalty keeps running until you pay or hit its own 25-percent ceiling.
Interest
Interest accrues on unpaid tax, penalties, and previously accrued interest, compounded daily. The rate resets quarterly at the federal short-term rate plus three percentage points. For the first quarter of 2026, the individual underpayment rate is 7 percent.4Internal Revenue Service. Quarterly Interest Rates Interest has no cap and runs until the balance is paid in full.
The practical takeaway is that filing now stops the failure-to-file penalty from growing, even if you can’t pay the tax yet. That’s the largest of the three charges, and it stops the moment the return is filed.
Refunds Have a Three-Year Deadline
If one of your unfiled years would have produced a refund, you have to file within three years of that return’s original due date to collect it. After three years, the money is permanently forfeited to the U.S. Treasury.5Internal Revenue Service. Filing Past Due Tax Returns The same cutoff applies to refundable credits such as the Earned Income Credit.
A 2022 return was originally due April 18, 2023, so a refund claim for that year generally has to be filed by April 18, 2026. If you had a valid extension for that year, the three-year window runs from the extended deadline instead.6Internal Revenue Service. Time You Can Claim a Credit or Refund
When you’re catching up on two years, work the refund year first if its deadline is closing in. A year where you owe tax has no filing cutoff for what you owe — penalties and interest just keep accumulating — but a refund year has a hard, unrecoverable expiration.7Office of the Law Revision Counsel. 26 USC 6511 – Limitations on Credit or Refund
Gathering Documents for Both Years
For each year, collect every income statement and deduction record that year produced:
- W-2 forms from each employer, showing wages and withholding for that specific year.
- 1099 forms in their various flavors: 1099-NEC for freelance income, 1099-INT for interest, 1099-DIV for dividends, 1099-R for retirement distributions.
- Deduction records dated to that year: mortgage interest statements, property tax bills, tuition receipts, charitable donation records, HSA contributions.8Internal Revenue Service. Gather Your Documents
If original W-2s or 1099s are missing, request a Wage and Income Transcript from the IRS. The transcript lists the income documents employers and financial institutions reported to the agency, and it’s available for the current year plus the nine prior tax years. You can request it online through your IRS account, by phone, or by mail.9Internal Revenue Service. Transcript Types for Individuals and Ways to Order Them
If an employer is out of business or unreachable and the transcript doesn’t fill the gap, Form 4852 works as a substitute W-2. You estimate wages from pay stubs, bank deposits, or any other records you have, and attach the form to the return with your calculations.10Internal Revenue Service. Form 4852, Substitute for Form W-2, Wage and Tax Statement, or Form 1099-R Before going that route, call the IRS at 800-829-1040; the agency may be able to obtain the missing form from the employer for you.
How to Submit Both Returns
E-Filing the Recent Ones
Most tax software supports e-filing for the current year plus the two immediately preceding years. Once the IRS opens e-filing for 2025 returns, you can electronically submit 2025, 2024, and 2023.11Internal Revenue Service. Electronic Filing (E-File) Anything older has to be filed on paper. The IRS has been gradually expanding prior-year e-filing, but for now older returns are exempt from the electronic filing requirement.12Internal Revenue Service. Frequently Asked Questions: E-File Requirements for Specified Tax Return Preparers
Mailing Paper Returns
If you’re mailing, each year’s return goes in its own envelope, or into a single larger envelope with each year’s return and supporting documents clipped together separately so the IRS can tell them apart. The correct mailing address depends on your state and whether you’re enclosing a payment; the IRS maintains a directory of addresses on its site.13Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment
Send by certified mail with return receipt. That gives you dated proof of delivery if the IRS later questions whether or when your return arrived. Keep a full copy of each completed return and every supporting document.
If You Can’t Pay What You Owe
Filing and paying are two separate obligations. File both returns even if you have no money to send with them; the failure-to-file penalty stops the moment the return is in, and the IRS won’t approve any payment arrangement until every required return is filed.
Short-Term Payment Plans
With a combined balance of tax, penalties, and interest under $100,000, you can request up to 180 days to pay in full. There’s no setup fee for a short-term plan whether you apply online or by phone.14Internal Revenue Service. Payment Plans; Installment Agreements Interest and the failure-to-pay penalty keep running during the window, but the total cost is lower than doing nothing.
Long-Term Installment Agreements
For balances that need more time, the IRS offers monthly installments over up to 10 years. Individuals with $50,000 or less in combined tax, penalties, and interest can apply online.15Internal Revenue Service. Simple Payment Plans for Individuals and Businesses Setup fees depend on how you apply and how you pay:
- Direct debit, applied online: $22
- Direct debit, applied by phone or mail: $107
- Other payment methods, applied online: $69
- Other payment methods, applied by phone or mail: $178
- Low-income taxpayers: setup fee waived for direct debit plans, or reduced to $43 for other payment methods14Internal Revenue Service. Payment Plans; Installment Agreements
On an approved plan paid by automatic bank withdrawal, the failure-to-pay penalty drops from 0.5 percent per month to 0.25 percent for the life of the agreement.3Internal Revenue Service. Failure to Pay Penalty
First-Time Penalty Abatement
If you’ve been compliant in prior years, you may qualify to have the failure-to-file or failure-to-pay penalty waived for a single tax year. Eligibility requires that you filed all required returns for the three years before the penalty year and had no penalties during that period (or any prior penalty was removed for an acceptable reason).16Internal Revenue Service. Administrative Penalty Relief It applies to one year at a time, so with two overdue returns you can use it to cut the cost of the more expensive one.
State Returns Aren’t Included
Most states with an income tax expect their own separate return for each year you were required to file, and state penalties, interest rates, and refund deadlines differ from the federal ones. When you catch up on federal returns, check whether the same years are open on the state side. Many state returns pull figures from the federal return, so finishing the federal filings first usually makes the state work simpler.