Tax Write-Off Limits: SALT, Mortgage, Charitable, and Section 179

Tax write-off limits for 2026 range from a $16,100 standard deduction for single filers to a $2,560,000 cap on Section 179 business expensing, with several ceilings reshaped by the One Big Beautiful Bill Act. Some limits are flat dollar amounts, others are percentages of your adjusted gross income, and a few phase down as your income rises. The list below covers what each major deduction tops out at and the conditions attached to it.

Standard Deduction

The standard deduction is the flat amount you can subtract from income without itemizing or keeping receipts. For 2026:

  • Single filers: $16,100
  • Married filing jointly: $32,200
  • Head of household: $24,150
  • Married filing separately: $16,100

These figures reflect the IRS inflation adjustments for 2026, which also incorporate changes from the One Big Beautiful Bill Act.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026

Filers who are 65 or older, or legally blind, add more on top. Single and head of household filers get an extra $2,050 per qualifying condition; married filers get $1,650 each. A couple where both spouses are over 65 adds $3,300 to their joint standard deduction. Itemizing only pays off if your total itemizable expenses exceed the standard deduction plus any age or blindness additions you qualify for.

State and Local Tax (SALT) Deduction

The SALT cap saw the biggest jump for 2026. The One Big Beautiful Bill Act raised the deduction limit from $10,000 to $40,000, with 1% annual increases scheduled through 2029. The cap covers state and local income taxes (or sales taxes, if you elect that instead) plus property taxes, and it applies equally to single filers and married couples filing jointly. Married filing separately gets $20,000.

High earners see the new cap phase down. Once adjusted gross income exceeds $500,000, the $40,000 limit shrinks by 30 cents for every dollar above that threshold, bottoming out at $10,000. The $500,000 phase-down threshold also rises 1% per year through 2029.

In practice, a homeowner paying $18,000 in property taxes and $14,000 in state income tax can now deduct the full $32,000 rather than the $10,000 allowed a year earlier. For many taxpayers earning under $500,000 in high-tax states, this change is enough to make itemizing worthwhile again.

Mortgage Interest Deduction

Interest on home acquisition debt is deductible up to a cap on the loan balance. For mortgages taken out after December 15, 2017, that cap is $750,000 ($375,000 for married filing separately). The One Big Beautiful Bill Act made this limit permanent.

Mortgages originated on or before December 15, 2017 remain under the older $1 million limit ($500,000 for married filing separately). Home equity loan interest is deductible only when the borrowed funds were used to buy, build, or substantially improve the home securing the loan. If total mortgage debt exceeds the applicable cap, only a proportional share of the interest is deductible.

Charitable Contribution Limits

Charitable deduction ceilings are set as percentages of adjusted gross income and vary by what you give and where:

Amounts above these ceilings aren’t lost. You can carry excess contributions forward for up to five additional tax years.2Office of the Law Revision Counsel. 26 USC 170 – Charitable, Etc., Contributions and Gifts

Documentation is strict. Any single donation of $250 or more needs a written acknowledgment from the recipient before you file, and non-cash property valued above $5,000 generally requires a qualified appraisal. Missing paperwork sinks the deduction regardless of whether the gift actually happened.

Medical Expense Deduction

Unreimbursed medical and dental expenses are deductible only to the extent they exceed 7.5% of adjusted gross income.4Office of the Law Revision Counsel. 26 USC 213 – Medical, Dental, Etc., Expenses At an $80,000 AGI, the first $6,000 in medical costs doesn’t count, and only dollars above that floor are deductible, and only if you itemize.

Qualifying costs include doctor visits, prescriptions, surgery, dental and vision care, mental health treatment, and health insurance premiums paid with after-tax dollars. Long-term care insurance premiums also qualify subject to age-based limits. Expenses reimbursed by insurance or paid through an HSA or FSA don’t count, since they’ve already received a tax benefit.

If you can’t clear the 7.5% hurdle, tax-advantaged health accounts offer a separate route. For 2026:

HSA contributions are deductible whether or not you itemize.

Retirement Contribution Limits

Retirement contributions reduce income before you decide whether to itemize, and the ceilings are among the largest available.

For 2026, the employee contribution limit for a 401(k), 403(b), or similar workplace plan is $24,500. Workers 50 and older can add $8,000 in catch-up contributions. A newer provision allows workers aged 60 through 63 a “super” catch-up of $11,250 instead of $8,000, if the employer’s plan permits it.5Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 The combined employee-plus-employer limit is $72,000.

Traditional IRA contributions cap at $7,500 for 2026, plus a $1,100 catch-up for those 50 and older.6Internal Revenue Service. Retirement Topics – IRA Contribution Limits The traditional IRA deduction phases out at higher incomes when you or your spouse are covered by a workplace plan. If neither spouse has workplace coverage, the full contribution is deductible regardless of income. Roth IRA contributions are never deductible.

Student Loan Interest Deduction

Borrowers can deduct up to $2,500 in qualified student loan interest per year, and this write-off is available even without itemizing.7Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction The full deduction for 2026 goes to single filers with modified adjusted gross income of $85,000 or less, phasing out completely at $100,000. Joint filers get the full amount up to $175,000 in MAGI, with the deduction gone at $205,000. Married filing separately cannot claim it at all.

Educator Expenses

K-12 educators can deduct up to $350 for 2026 in unreimbursed classroom supplies, or $700 on a joint return where both spouses qualify. Qualifying purchases include books, supplies, computer equipment, supplementary materials, and professional development courses. No itemizing or minimum spending is required.

Capital Loss Deduction

Investment losses offset investment gains dollar for dollar with no cap. Net losses beyond your gains can be deducted against ordinary income up to $3,000 per year, or $1,500 if married filing separately.8Internal Revenue Service. Topic No. 409, Capital Gains and Losses That $3,000 ceiling has held since 1978 and is not indexed for inflation.

Losses exceeding $3,000 carry forward indefinitely, keeping their character as short-term or long-term. A $15,000 loss with no offsetting gains works down at $3,000 per year for five years. The carryforward never expires.

Business and Self-Employment Write-Offs

The limits change substantially once you’re deducting on the business side.

Section 179 Expensing

Section 179 lets a business write off the full cost of qualifying equipment, vehicles, and software in the year of purchase rather than depreciating over time. For 2026, the maximum deduction is $2,560,000. It phases out dollar for dollar once total equipment purchases exceed $4,090,000, effectively reserving the benefit for small and mid-sized businesses. Equipment must be placed in service during the same tax year and used for business more than 50% of the time.

Business Meals

The general deduction for business meals in 2026 is 50% of the cost, if there’s a clear business purpose and the meal isn’t lavish. Entertainment expenses remain fully nondeductible. Starting in 2026, meals provided at employer-operated cafeterias and meals offered for the employer’s convenience on business premises are also nondeductible. Company holiday parties and employee social events stay 100% deductible.

Self-Employment Tax Deduction

Self-employed workers pay both halves of Social Security and Medicare tax. You can deduct the employer-equivalent half when calculating adjusted gross income.9Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) The deduction is automatic and doesn’t require itemizing. It won’t reduce the self-employment tax itself, but it lowers your income tax.

Every business deduction demands documentation. Meals require the date, amount, business purpose, and attendees. Equipment purchases need invoices showing the placed-in-service date. Penalties for overstating deductions run from 20% of the underpayment for negligence up to 75% for fraud.