Line 12 on Form 1040 is where you enter the deduction that gets subtracted from your adjusted gross income to produce your taxable income. You put one of two numbers there: the standard deduction for your filing status, or the total of your itemized deductions from Schedule A. Whichever is larger is the one that belongs on the line.
Where Line 12 Sits on the Form
Your AGI is calculated earlier on the return. Line 12 comes next, and it reduces that AGI. The result flows to Line 15 as taxable income, which is the figure the tax brackets actually run against. Every dollar you put on Line 12 is a dollar the IRS doesn’t tax.
Most filers take the standard deduction. It requires no receipts, no Schedule A, and no math beyond looking up the amount for your filing status. Itemizing only pays off when your qualifying expenses add up to more than that standard amount.
Standard Deduction Amounts for 2026
The IRS adjusts these figures for inflation each year. For the 2026 tax year:
- Single: $16,100
- Married filing jointly: $32,200
- Head of household: $24,150
- Married filing separately: $16,100
If none of the situations below apply to you, one of these numbers goes directly onto Line 12.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill
The Extra Deduction if You’re 65 or Older or Blind
Filers age 65 or older, or who are legally blind, have long qualified for a small additional standard deduction on top of the base amount. That add-on is inflation-adjusted and generally runs about $1,500 to $2,000 depending on filing status.
Starting with the 2025 tax year and running through 2028, the One Big Beautiful Bill Act added a further enhanced deduction of $6,000 for qualifying seniors. A married couple filing jointly with both spouses 65 or older can claim $12,000. That stacks on top of the base standard deduction and the existing age or blindness add-on. A single filer over 65 can see a total standard deduction well above $22,000 for 2026, which raises the bar for itemizing considerably. Form 1040-SR, the large-print version available to filers 65 and older, uses the same Line 12 and the same schedules.2Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return
When You Can’t Take the Standard Deduction
A few filers have to itemize whether or not the numbers favor it. The most common: if you’re married filing separately and your spouse itemizes, you must itemize too. Nonresident aliens generally can’t take the standard deduction either. If that’s you, your Line 12 amount will always come from Schedule A.
Itemizing on Schedule A
When your qualifying expenses beat the standard deduction, you file Schedule A and the total flows to Line 12.3Internal Revenue Service. Topic No. 501, Should I Itemize? Four categories drive most itemized returns.
State and Local Taxes
You can deduct state and local income taxes (or sales taxes, but not both) plus property taxes. The $10,000 SALT cap that took effect in 2018 was raised substantially by the One Big Beautiful Bill Act. For the 2026 tax year, the limit is approximately $40,400 for single and joint filers, indexed at 1% annually. Married filing separately gets half. This change is the main reason some taxpayers who stopped itemizing after 2017 should rerun the numbers.
Mortgage Interest
Interest on a mortgage used to buy, build, or substantially improve your primary or second home is deductible on the first $750,000 of qualifying debt, or $375,000 if married filing separately. That limit is now permanent. Beginning in 2026, private mortgage insurance premiums also qualify as deductible mortgage interest for eligible filers.
Medical and Dental Expenses
Medical costs are deductible only to the extent they exceed 7.5% of your AGI. At $80,000 in AGI, only the portion above $6,000 counts. This threshold is hard to clear without either a major medical event or a combination of modest income and high ongoing costs.
Charitable Contributions
Donations to qualified charities remain deductible when you itemize, but 2026 brings a floor: only the portion of your total contributions above 0.5% of your AGI is deductible. At $100,000 AGI, the first $500 in donations produces no itemized deduction. Cash gifts to public charities are generally capped at 60% of AGI, with tighter caps on non-cash property.
How Line 12 Changes Your Tax
The arithmetic is simple. AGI minus Line 12 equals taxable income. A single filer with $75,000 in AGI who takes the $16,100 standard deduction lands at $58,900 in taxable income. If that same filer had $22,000 in itemized deductions instead, taxable income drops to $53,000, saving roughly $1,300 at the 22% bracket.
The New Charitable Deduction for Non-Itemizers
For 2026, taxpayers who take the standard deduction can still claim a limited charitable deduction on top of it. Cash contributions to qualifying charities are deductible up to $1,000, or $2,000 for joint filers, without filing Schedule A. If you give modest amounts each year but don’t have enough total expenses to itemize, this puts a small but real benefit on the table.
Fixing a Wrong Line 12
If you realize you picked the wrong deduction method or miscalculated your Schedule A, file Form 1040-X to correct it. You’ll show the original amounts, the changes, and the corrected figures, with a written explanation.4Internal Revenue Service. Instructions for Form 1040-X Amended U.S. Individual Income Tax Return
To claim a refund, you generally have three years from the date you filed the original return or two years from the date you paid the tax, whichever is later. If the IRS catches the error first, the standard accuracy-related penalty is 20% of the underpayment.5Office of the Law Revision Counsel. 26 USC 6662A – Imposition of Accuracy-Related Penalty on Understatements With Respect to Reportable Transactions An isolated math error, reliance on a tax professional’s advice, or reliance on an incorrect W-2 or 1099 can qualify as reasonable cause for relief, but you have to demonstrate you exercised ordinary care.
Records to Keep Behind Your Deduction
The documents that support your Line 12 number need to outlast most people’s filing habits. The general rule is three years from the filing date, which covers the standard audit window. If you underreported income by more than 25% of gross income, the IRS has six years. Claims involving worthless securities or bad debt require seven.6Internal Revenue Service. How Long Should I Keep Records
For itemizers, that means holding mortgage interest statements, property tax bills, medical receipts, and charitable donation records for at least three years after filing. Charitable contributions of $250 or more require a written acknowledgment from the organization stating the amount and whether you received anything in return.7Internal Revenue Service. Charitable Contributions: Written Acknowledgments