How to Fill Out Schedule A (Form 1040): Itemized Deductions Line by Line

To fill out Schedule A on Form 1040, work through six categories of deductible personal expenses — medical costs, state and local taxes, mortgage interest, charitable gifts, casualty losses, and a short list of other items — and carry the combined total on Line 18 back to Form 1040 in place of the standard deduction. The form only helps you if that total beats the standard deduction for your filing status: $16,100 single, $32,200 married filing jointly, or $24,150 head of household for 2026.¹

Confirm Itemizing Is Worth Your Time

Before entering a single number, add up rough totals for each of the six categories and compare the sum to your standard deduction. If your itemized total is smaller, skip Schedule A and take the standard deduction on Form 1040. If it’s larger, the form is worth completing.² Taxpayers with sizable mortgages, high state and property taxes, or significant charitable giving are the ones who most often clear the threshold.

Gather Your Records First

Each category has its own paper trail. Pull these together before opening the form:

Medical receipts, insurer explanation-of-benefits statements, and a mileage log for medical travel.
W-2s showing state and local income tax withheld, property tax bills, and receipts for major purchases if you’re claiming sales tax.
Form 1098 from every mortgage lender, including a separate 1098 for any second mortgage or HELOC.³
Bank records for cash gifts, and written acknowledgment letters from any charity you gave $250 or more in a single contribution.⁴
Insurance claims, police reports, and any FEMA disaster declaration number for casualty losses.

Lines 1–4: Medical and Dental Expenses

Only the portion of unreimbursed medical spending that exceeds 7.5% of your adjusted gross income is deductible.⁵ With an AGI of $80,000, that means the first $6,000 of medical costs produces no deduction at all.

Enter total qualifying expenses on Line 1. Qualifying costs include payments to doctors, surgeons, dentists, and other practitioners; prescription drugs and insulin; eyeglasses, hearing aids, and medical equipment; and health insurance premiums you paid out of pocket rather than through a pre-tax employer plan. Subtract anything your insurance reimbursed before you enter the total.

Medical travel counts too. For 2026, the rate is 20.5 cents per mile driven to and from medical appointments, plus parking and tolls.⁶ Lodging away from home for treatment is deductible up to $50 per night per person.⁷

Line 2 is your AGI from Form 1040. Line 3 multiplies that by 0.075. Line 4 subtracts Line 3 from Line 1. If the result is zero or negative, the medical deduction is zero.

Lines 5–7: State and Local Taxes (SALT)

The SALT deduction covers state and local income tax (or sales tax), real estate tax, and personal property tax, capped at a combined $40,000 for 2026, or $20,000 if you’re married filing separately.⁸

High earners face a phasedown. If your modified adjusted gross income exceeds $500,000, the $40,000 cap shrinks by 30 cents for every dollar of excess MAGI, with a floor of $10,000 ($5,000 for married filing separately).⁸ MAGI of $600,000 puts you $100,000 over the threshold, cuts the cap by $30,000, and lands you at a $10,000 limit.

On Line 5a, pick either state and local income tax or general sales tax — you cannot claim both. Filers in states with an income tax usually do better with income tax; residents of states without one, such as Texas, Florida, or Washington, use sales tax. Line 5b takes real estate taxes. Line 5c handles personal property taxes such as value-based vehicle registration fees. Line 7 totals these, capped at your applicable limit.

Lines 8–10: Home Mortgage Interest

Report interest from Box 1 of each Form 1098 on Line 8a.⁹ For mortgages taken out after December 15, 2017, interest is deductible on up to $750,000 of home acquisition debt, or $375,000 if married filing separately.¹⁰ Loans originated on or before that date remain grandfathered at $1 million as long as you haven’t refinanced into a larger principal balance.

The debt must be secured by your main home or a second home, and the money must have gone to buy, build, or substantially improve that home. HELOC interest qualifies only when the funds were used for qualifying home improvements; borrowing against your home to pay off credit cards or buy a car does not produce a deductible interest expense. If you carry loans on two homes, the $750,000 ceiling applies to the combined balance.¹⁰

Points paid to acquire your main home are generally deductible in full in the year of purchase on Line 8c. Points paid on a refinance are amortized over the life of the loan.

Lines 11–14: Charitable Contributions

Cash gifts to qualified charities go on Line 11. Noncash gifts — clothing, household goods, appreciated stock, vehicles — go on Line 12. Line 13 pulls in any carryover from prior years when your donations exceeded the AGI-based limits.

Those limits depend on the type of gift and the type of recipient. Cash to a public charity is deductible up to 60% of AGI. Noncash property to a public charity is generally limited to 50%, dropping to 30% for appreciated capital gain property such as stock held more than a year. Gifts to private foundations top out at 30% for cash and 20% for capital gain property.¹¹ Amounts above the applicable ceiling carry forward for up to five years.

Documentation rules tighten as the gift grows. Any single cash contribution of $250 or more requires a written acknowledgment from the charity showing the amount, the date, and whether you received anything in return.⁴ Noncash donations totaling more than $500 require Form 8283, Section A.¹² Any single item or group of similar items valued above $5,000 needs a qualified independent appraisal and Form 8283, Section B, signed by the charity.¹³ Skipping the appraisal on a large noncash gift is one of the most common reasons the IRS disallows a charitable deduction. Donated clothing and household items must be in good used condition or better.

Line 15: Casualty and Theft Losses

Personal casualty and theft losses are deductible only when the loss stems from a federally declared disaster, and beginning in 2026, certain state-declared disasters also qualify under the One Big Beautiful Bill Act.¹⁴ An ordinary break-in or storm damage without a declaration produces no deduction on Line 15.

One narrow exception: if you have personal casualty gains (usually because insurance proceeds exceeded your basis in the damaged property), you can deduct personal casualty losses up to the amount of those gains even without a disaster declaration. Compute the loss on Form 4684 and bring the result to Line 15.

Line 16: Other Itemized Deductions

Line 16 catches items that don’t fit the earlier categories. The most common entry is gambling losses, deductible only up to reported gambling winnings. Starting in 2026, the deduction is limited to 90% of losses, not the full amount. Win $10,000 and lose $10,000, and you owe tax on $1,000 of gambling income because your deductible loss caps at $9,000. There’s no carryforward for the unused 10%.

A handful of unreimbursed employee expense categories also survive here for specific workers: Armed Forces reservists who travel more than 100 miles for reserve duties, qualified performing artists meeting the statute’s income and employer tests, fee-based state and local government officials, and employees with disability-related work expenses. For every other employee, unreimbursed business expenses remain nondeductible at the federal level. Amortizable bond premiums and certain deductions related to income in respect of a decedent can also land on Line 16. Most filers leave it blank.

Line 17–18: Total and Transfer to Form 1040

Line 17 sums the six category totals. Line 18 restates that total as your itemized deduction, which then replaces the standard deduction on Form 1040 (Line 12 on the current form).⁵ Before transferring, check the arithmetic in each section against your source documents. Software users should still review the populated figures; the program only knows what you typed in.

Schedule A is filed as part of Form 1040, not separately. E-filing software packages it automatically. Paper filers attach Schedule A directly behind Form 1040.

Keep the Backup

Hold every receipt, acknowledgment letter, Form 1098, and bank statement supporting Schedule A for at least three years from the filing date, which matches the general statute of limitations for an IRS audit.¹⁵ If income was underreported by more than 25%, the IRS has six years, and there’s no time limit on fraudulent returns. Legible digital copies are acceptable.

Penalty for Overstating Deductions

Inflating Schedule A entries, whether by intent or sloppy records, can trigger the accuracy-related penalty under IRC Section 6662: 20% of the underpayment caused by the overstatement, regardless of whether the IRS labels it negligence, disregard of rules, or a substantial understatement.¹⁶ The penalty can be waived for reasonable cause and good faith, which generally means documented reliance on competent professional advice or a genuine effort to follow the rules. Claim only what you can document, and check the Schedule A instructions whenever you’re unsure whether an expense qualifies.⁵

1
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
2
Internal Revenue Service. About Schedule A (Form 1040), Itemized Deductions
3
Internal Revenue Service. Instructions for Form 1098 – Mortgage Interest Statement
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Internal Revenue Service. Charitable Contributions: Written Acknowledgments
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Internal Revenue Service. Instructions for Schedule A (Form 1040)
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Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile, Up 2.5 Cents
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Internal Revenue Service. Publication 502 (2025), Medical and Dental Expenses
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Internal Revenue Service. Topic No. 503, Deductible Taxes
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Internal Revenue Service. Form 1098 – Mortgage Interest Statement
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Internal Revenue Service. Publication 936 – Home Mortgage Interest Deduction
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Office of the Law Revision Counsel. 26 USC 170 – Charitable, Etc., Contributions and Gifts
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Internal Revenue Service. About Form 8283, Noncash Charitable Contributions
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Internal Revenue Service. Publication 526 (2025), Charitable Contributions
14
Internal Revenue Service. Topic No. 515, Casualty, Disaster, and Theft Losses
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Internal Revenue Service. How Long Should I Keep Records
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Internal Revenue Service. Accuracy-Related Penalty