If the calendar has already turned, you still have real ways to lower your AGI after year end. Federal tax law lets you make certain retirement and health savings contributions after December 31 and count them against the prior year’s income. A traditional IRA deposit, a Health Savings Account contribution, and, for the self-employed, a SEP IRA or newly adopted solo 401(k) can each cut your adjusted gross income dollar for dollar. That can drop you into a lower bracket, restore credits that phase out at higher incomes, and shrink the check you write in April.
Traditional IRA Contributions
The most accessible retroactive move is a traditional IRA contribution. The deposit is treated as if made on the last day of the prior tax year, provided it lands in the account by the filing deadline, typically April 15.1Office of the Law Revision Counsel. 26 USC 219 – Retirement Savings Filing an extension does not extend this deadline. You get until April 15 even if you push your return to October.
For the 2026 tax year, the limit is $7,500 if you’re under 50 and $8,600 if you’re 50 or older.2Internal Revenue Service. Retirement Topics – IRA Contribution Limits You need earned income at least equal to what you put in, and every deductible dollar reduces your AGI one for one.
The deduction phases out if you’re covered by a workplace retirement plan. For 2026, single filers lose the deduction between a modified AGI of $81,000 and $91,000. Joint filers with a workplace plan phase out between $129,000 and $149,000. If you don’t have a workplace plan but your spouse does, the range is $242,000 to $252,000. Married filing separately runs from $0 to $10,000.3Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs If neither spouse has an employer plan, the full deduction is available at any income level.
These thresholds use modified AGI, not plain AGI. For traditional IRA purposes, MAGI adds back the IRA deduction itself, the student loan interest deduction, and any foreign earned income exclusion.4Internal Revenue Service. Modified Adjusted Gross Income For most W-2 earners, MAGI and AGI come out roughly the same.
Spousal IRA Contributions
On a joint return, the working spouse’s compensation can support contributions to both spouses’ IRAs when one spouse has little or no earned income. Each account can receive up to the full annual limit as long as combined taxable compensation covers the total.2Internal Revenue Service. Retirement Topics – IRA Contribution Limits That doubles the household’s retroactive AGI reduction. Same April 15 cutoff, same phase-out rules.
HSA Contributions
If you had a High Deductible Health Plan during the prior year, a retroactive HSA contribution is another strong lever. Deposits made by April 15 count toward the prior tax year, and extensions do not buy extra time.5Office of the Law Revision Counsel. 26 USC 223 – Health Savings Accounts
For 2026, the ceiling is $4,400 for self-only HDHP coverage and $8,750 for family coverage. If you’re 55 or older and not on Medicare, you can add another $1,000.6Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans The contribution reduces AGI dollar for dollar with no income-based phase-out, so high earners who lose the IRA deduction can still take the full HSA deduction.
To qualify, your plan must meet the 2026 HDHP definition: a minimum annual deductible of $1,700 self-only or $3,400 family, and out-of-pocket maximums no higher than $8,500 self-only or $17,000 family.7Internal Revenue Service. Expanded Availability of Health Savings Accounts You can’t be enrolled in Medicare or claimed as someone else’s dependent.
The Last-Month Rule
Joined an HDHP partway through the year? You may still get the full annual contribution. Under the last-month rule, being HDHP-eligible on December 1 lets you contribute as though you had coverage for all twelve months.6Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans The catch: you must stay HDHP-eligible through December 31 of the following year. Dropping coverage during that 13-month testing period for any reason other than death or disability triggers income inclusion of the extra amounts plus a 10% penalty.
Self-Employed Options
Self-employed filers get the most generous retroactive window. A Simplified Employee Pension IRA can be established and funded as late as the due date of your return, including extensions.8Internal Revenue Service. Retirement Plans FAQs Regarding SEPs File an extension by April 15 and you have until October 15 to open the account and deposit the money.
For 2026, the maximum SEP contribution is the lesser of 25% of compensation or $72,000.9Internal Revenue Service. SEP Contribution Limits For a sole proprietor, the effective ceiling is closer to 20% of net self-employment earnings because the contribution is itself deductible, creating a circular calculation the IRS resolves with a reduced-rate table.10Internal Revenue Service. Publication 560, Retirement Plans for Small Business Start with net Schedule C profit, subtract half of your self-employment tax, then apply the reduced rate.11Internal Revenue Service. Self-Employed Individuals – Calculating Your Own Retirement Plan Contribution and Deduction Even at the reduced rate, a sole proprietor with $200,000 in net earnings can shelter roughly $37,000 in one move.
Solo 401(k) Under SECURE 2.0
SECURE 2.0, Section 317, lets sole proprietors and single-member LLCs with no employees other than the owner adopt a brand-new solo 401(k) retroactively, so long as the plan is in place by the tax filing deadline without extensions, typically April 15. Before this change, the plan had to exist by December 31.
The advantage over a SEP is the employee deferral. You contribute as the employer (up to roughly 20 to 25% of compensation) and as the employee through elective deferrals. For 2026, the employee deferral limit is $24,500, with an $8,000 catch-up for ages 50 to 59 or 64 and older, and $11,250 for ages 60 to 63. The combined limit is $72,000 for those under 50.3Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs A self-employed person in their early sixties could shelter over $83,000 in a single year.
Two limits on this retroactive route. It applies only in the plan’s first year. And unlike the SEP deadline, the solo 401(k) adoption deadline does not extend with a tax extension.
The Saver’s Credit Stack
Lowering your AGI through a retroactive contribution can trigger a second benefit: the Retirement Savings Contributions Credit, or Saver’s Credit. It’s a direct tax credit worth up to 50% of the first $2,000 you contribute to an IRA or employer plan, scaled by income. For 2026, it’s available to joint filers with AGI up to $80,500, heads of household up to $60,375, and single filers up to $40,250.12Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
A retroactive IRA contribution can do double duty. It reduces AGI and qualifies as the contribution triggering the credit. If your income sits just above a threshold, the deduction may pull you below the cutoff and unlock the credit in the same move. Run the numbers before you file.
Avoiding Excess Contribution Penalties
Retroactive contributions carry a steep penalty if you overshoot: a 6% excise tax on the excess for every year it remains in the account.6Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans That applies to both IRAs and HSAs. A $1,000 excess left alone for three years costs $180 in penalties.
You avoid the tax by withdrawing the excess plus any earnings before your filing deadline, including extensions. The withdrawn earnings are taxable in the year you pull them out. Miss the correction window and the 6% recurs annually until you fix it, either by withdrawal or by applying the excess against the next year’s limit.
Getting the Contribution Reported to the Right Year
All three deductions are above-the-line adjustments on Schedule 1 of Form 1040, feeding into line 11 (your AGI) on the main form.13Internal Revenue Service. Schedule 1 (Form 1040), Additional Income and Adjustments to Income
When you make the deposit, tell the bank or brokerage explicitly that it’s a prior-year contribution and name the tax year. The institution uses that designation to generate Form 5498, which reports the contribution to the IRS under the correct year.14Internal Revenue Service. Form 5498, IRA Contribution Information Form 5498 often isn’t mailed until May, so the IRS is matching your return against a document that arrives later. If the years don’t match because you forgot to specify, expect a notice.
Keep the deposit confirmation showing the transfer date and the prior-year designation. If the IRS questions the timing, a bank statement and written confirmation of the year designation are usually enough to close the question.