Definition
Itemized deductions are eligible expenses you can deduct from your gross income on Schedule A of your federal return, in place of the standard deduction. Common itemized deductions include mortgage interest, state and local taxes (SALT, capped at $40,400 in 2026 under OBBBA and reduced for incomes above $505,000), charitable contributions, and significant medical expenses above 7.5% of AGI.
You itemize when your total qualifying deductions exceed the standard deduction amount for your filing status. This is most common for homeowners with large mortgages, residents of high-tax states, or those with significant charitable giving.
Under OBBBA, the SALT cap was raised from $10,000 to $40,000 for 2025 and $40,400 for 2026 (it is scheduled to return to $10,000 in 2030), making itemizing more valuable for many homeowners in states like California, New York, and New Jersey.
How this affects your W-4
If you itemize and your total deductions exceed the standard deduction, enter the excess in W-4 Step 4b. This reduces your annual withholding dollar-for-dollar for the difference.
For example, if you're a single filer with $35,000 in itemized deductions, your Step 4b entry is $35,000 − $16,100 = $18,900. This tells your employer to withhold less because you'll owe less tax.
See how itemized deductions affects your withholding
Use the free W-4 calculator to calculate your exact withholding with your specific situation.
Open the W-4 Calculator →Read the guide
How Buying a Home Affects Your W-4 (2026 Guide)
New mortgage = potential itemized deductions. Here's when the numbers clear the 2026 standard deduction bar — and how to capture the savings in Step 4b.
W-4 Step 4 Explained: Other Income, Deductions, and Extra Withholding (2026)
Step 4 is how you fine-tune for side income, itemized deductions, and extra withholding. Most people skip it — here's when you shouldn't.
Related terms
Standard Deduction
A flat dollar amount that reduces your taxable income — most taxpayers take this instead of itemizing.
SALT Deduction
The deduction for state and local taxes paid — capped at $40,000 under OBBBA ($40,400 for 2026), up from $10,000.
Deductions Worksheet
The worksheet on the W-4 (page 4) whose line 15 total goes in Step 4(b): itemizing above the standard deduction, tips, overtime, car loan interest, seniors, student loan interest and more.