A tax deduction phase-out is a rule that gradually reduces the dollar amount you can deduct once your income passes a set threshold, shrinking the deduction across a defined range instead of cutting it off all at once. The point is to keep a modest raise from triggering a sudden tax cliff. Most phase-outs are tied to your adjusted gross income or modified adjusted gross income, and the income thresholds change each year with inflation.
The Income Figure That Triggers a Phase-Out
Almost every phase-out starts with a single number: adjusted gross income. AGI is your total income minus a specific list of “above-the-line” deductions like educator expenses, self-employment tax, and retirement contributions.1Office of the Law Revision Counsel. 26 USC 62 – Adjusted Gross Income Defined It’s your income after the adjustments you can take whether or not you itemize.
Many phase-outs use a slightly different figure, modified adjusted gross income. MAGI starts with your AGI and adds back certain excluded items like foreign earned income or tax-exempt interest.2Internal Revenue Service. Modified Adjusted Gross Income The add-backs stop someone from sheltering income through exclusions and then claiming deductions meant for lower earners. The exact MAGI formula varies by deduction, so the instructions for each one tell you what to add back.
How Filing Status Changes the Threshold
Filing status sets the exact income where a phase-out begins. Joint filers nearly always get higher thresholds than single filers, reflecting a household’s combined earnings. Head of household filers sometimes have their own thresholds and sometimes share the single-filer range, depending on the deduction.
Married couples filing separately are treated harshly. For several major deductions, including the student loan interest deduction and the traditional IRA deduction, married-filing-separately filers get no deduction regardless of income.3Office of the Law Revision Counsel. 26 USC 219 – Retirement Savings If you’re considering separate returns, check whether the deductions you’d forfeit outweigh whatever you gain by filing apart.
The IRS adjusts most phase-out thresholds annually for inflation, which keeps deductions from eroding just because wages rose with prices.4Internal Revenue Service. Inflation-Adjusted Tax Items by Tax Year Updated figures usually appear in the fall for the following tax year, giving you time to plan if your income is near a threshold.
How To Calculate a Partial Deduction
When your income lands inside a phase-out range, you get a reduced deduction rather than nothing. The math needs three numbers: your MAGI, the phase-out floor, and the phase-out ceiling.
Subtract the floor from your MAGI. Divide that result by the width of the range (ceiling minus floor). That fraction is the portion of the deduction you lose. Multiply the maximum deduction by that fraction, and subtract from the maximum. What’s left is your allowed deduction.
For a single filer with $90,000 in MAGI claiming the student loan interest deduction, income sits $5,000 above the $85,000 floor. The phase-out range is $15,000 wide ($100,000 ceiling minus $85,000 floor). One-third of the range is used, so one-third of the $2,500 maximum is lost. The deduction drops to roughly $1,667.5Internal Revenue Service. Revenue Procedure 2025-32 The IRS supplies worksheets in the instructions for each affected form, so you don’t need to memorize the formula, but knowing the logic helps you estimate where you’ll land before filing season.
Common Deductions That Phase Out in 2026
Several widely claimed deductions shrink or disappear once income exceeds specific limits. The figures below are 2026 amounts, and because these numbers change every year, confirm the current thresholds before you file.
Student Loan Interest
You can deduct up to $2,500 in interest on qualified education loans, but the deduction starts shrinking once MAGI exceeds $85,000 for single filers or $175,000 for joint filers. It disappears entirely at $100,000 for single filers and $205,000 for joint filers.5Internal Revenue Service. Revenue Procedure 2025-32 Married filing separately filers can’t claim it at all. The deduction is above-the-line, so you don’t need to itemize.6Office of the Law Revision Counsel. 26 US Code 221 – Interest on Education Loans
Traditional IRA Contributions
The rules depend on whether you or your spouse participate in an employer retirement plan like a 401(k). If you do, the 2026 phase-out ranges for deducting traditional IRA contributions are:
- Single filer covered by a workplace plan: MAGI between $81,000 and $91,000.
- Joint filer where the contributing spouse is covered: MAGI between $129,000 and $149,000.
- Married filer not covered, but whose spouse is covered: MAGI between $242,000 and $252,000.
Below the floor of each range, the full contribution is deductible. Above the ceiling, nothing is deductible.7Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 If neither spouse participates in a workplace plan, there is no phase-out, and the full IRA contribution is deductible regardless of income.3Office of the Law Revision Counsel. 26 USC 219 – Retirement Savings Married filing separately filers covered by a workplace plan have a phase-out range of just $0 to $10,000, which eliminates the deduction for most people in that status.
Rental Real Estate Loss Allowance
If you actively manage rental property, you can normally deduct up to $25,000 in rental losses against other income even though rental activity is generally passive. The allowance phases out at a steep rate: 50 cents lost for every dollar of AGI above $100,000, with the full $25,000 gone at $150,000.8Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited These thresholds are not indexed for inflation and have been unchanged for decades. A landlord earning $125,000 would lose half the allowance and be limited to $12,500 in deductible rental losses.
Senior Deduction for Taxpayers 65 and Older
From 2025 through 2028, taxpayers who are at least 65 can claim an additional $6,000 deduction on top of the higher standard deduction already available to seniors. Married couples where both spouses qualify can claim $12,000.9Internal Revenue Service. One, Big, Beautiful Bill Provisions – Individuals and Workers It phases out for single filers with MAGI above $75,000 and joint filers above $150,000, at roughly six cents per dollar over the threshold. A single filer at $100,000 loses $1,500 and claims $4,500. The deduction is fully gone at $175,000 for single filers or $250,000 for joint filers.
Qualified Business Income Deduction
If you earn income through a sole proprietorship, partnership, or S corporation, you may qualify for a deduction of up to 20% of that qualified business income under Section 199A. For 2026, the phase-out range begins around $201,750 for single filers and $403,500 for joint filers. Inside the range, the deduction gets limited by wage and property tests. Service-based businesses like law firms, medical practices, and consulting firms face a tighter restriction: once income exceeds roughly $276,750 for single filers or $553,500 for joint filers, no QBI deduction is available for those businesses. Non-service businesses can still claim a reduced deduction above those thresholds, though the wage and property caps limit it.
SALT Deduction Cap
The state and local tax deduction is capped at $40,000 for 2026 ($20,000 for married filing separately), and the cap itself phases down for high earners. The $40,000 limit shrinks by 30 cents for every dollar of MAGI above $500,000 ($250,000 for married filing separately), but the deduction cannot fall below $10,000. Both the cap and the income threshold are indexed upward by 1% annually. In practical terms, the SALT deduction becomes a $10,000 deduction once MAGI climbs far enough past $500,000.
Ways To Stay Below a Phase-Out Threshold
Because phase-outs are keyed to AGI or MAGI, anything that lowers those figures preserves deductions that would otherwise shrink. The most accessible lever for most workers is maximizing pre-tax retirement contributions. For 2026, you can defer up to $24,500 into a traditional 401(k) or 403(b), plus an $8,000 catch-up if you’re 50 or older. Workers between 60 and 63 can contribute $11,250 in catch-up contributions instead of $8,000. Every dollar deferred reduces AGI dollar-for-dollar, which can push you below a phase-out floor or deeper into the reduced range.
Health savings accounts work similarly. If you have a high-deductible health plan, you can contribute up to $4,400 for self-only coverage or $8,750 for family coverage in 2026. HSA contributions are above-the-line, so they lower AGI the same way 401(k) deferrals do. Unlike most tax-advantaged accounts, HSAs have no income-based phase-out of their own.
Timing income and deductions across tax years is another common approach. If you expect a bonus or large capital gain that would push you into a phase-out range, deferring the income to the next year (when possible) can keep MAGI below the threshold. Bunching charitable contributions or other itemized deductions into alternating years can help manage AGI as well, though it takes planning.
Self-employed taxpayers have more flexibility. Contributing to a SEP-IRA or solo 401(k) reduces AGI, and the contribution limits are substantially higher than those for traditional IRAs. Timing business expenses, accelerating depreciation, or adjusting invoicing near year-end can also shift income between tax years. The key is knowing your phase-out thresholds early enough to act, rather than discovering in April that a deduction slipped away by a few thousand dollars.