How to Fill Out IRS Schedule 1-A: Step-by-Step Instructions
Schedule 1-A was just released by the IRS on March 2, 2026 (IR 2026-28), and guidance is limited. Here's your complete line-by-line walkthrough for claiming all OBBB deductions correctly.
What Is Schedule 1-A?
Schedule 1-A (Additional Adjustments to Income) is the IRS form specifically created for claiming deductions under the One Big Beautiful Bill Act. This single form handles five of the six OBBB tax benefits (the Child Tax Credit increase is automatic on Form 1040).
🎯 Key Insight
This is THE form everyone's been waiting for since OBBB passed. With very few guides available yet, mastering Schedule 1-A gives you a huge advantage in claiming your deductions quickly and correctly.
Schedule 1-A at a Glance
Form number: Schedule 1-A (Form 1040)
Title: Additional Adjustments to Income
Released: March 2, 2026
For tax year: 2025
Lines: 6 main lines + worksheets
Attaches to: Schedule 1, Line 8l
Final destination: Form 1040, Line 8
Software support: Rolling out mid-March
Before You Start: Documents You'll Need
Gather these documents before sitting down with Schedule 1-A. Having everything ready will save time and reduce errors:
Essential Documents
- • All W-2 forms (check Box 12 for OBBB codes)
- • 1098 forms for auto loan interest
- • State and local tax payment records
- • Birth certificates or SSA statements (if 65+)
- • Previous year's tax return (for MAGI calculation)
Supporting Records
- • Overtime hours and pay stubs
- • Tip income records (if not on W-2)
- • Auto purchase documentation (US-made verification)
- • Local tax bills (property, sales, income)
- • Spouse's age documentation (if married filing jointly)
⚠️ Pro Tip: Check Your W-2 Box 12
Look for these specific codes in Box 12 of your W-2: "OBBBTT" for overtime premium and "OBBBT" for tip income. These new codes make filling out Lines 1 and 2 much easier.
Line-by-Line Instructions
Line 1: Qualified Overtime Premium Pay Deduction
Enter the total amount of overtime premium pay you received in 2025. This is NOT your total overtime wages — only the premium amount above your regular hourly rate.
Where to Find This Amount:
- Option 1: W-2 Box 12, code "OBBBTT" (easiest method)
- Option 2: Calculate manually using pay stubs
- Option 3: Contact payroll if amount seems incorrect
Example Calculation:
Regular rate: $25/hour • Overtime rate: $37.50/hour • Premium: $12.50/hour
Overtime hours worked: 260 hours • Line 1 amount: $3,250
Line 2: Qualified Tip Income Deduction
Enter the amount of tip income you want to deduct. You can deduct up to 100% of tip income you received, subject to the $25,000 cap and income phase-outs.
Sources of Tip Income:
- W-2 Box 12 code "OBBBT": Tips reported to employer
- W-2 Box 1: May include some tip income (check with payroll)
- Cash tips: Tips you reported on Form 4137
- Credit card tips: Usually included in W-2 wages
⚠️ Important Note:
Only include tips you actually received. Don't include tip income you gave to other employees through tip pooling — those amounts shouldn't be on your W-2 anyway.
Line 3: Auto Loan Interest Deduction (US-Manufactured Vehicles)
Enter the interest you paid on loans for qualifying vehicles. The vehicle must be US-manufactured and have an MSRP under the income-based limits.
Qualifying Vehicle Requirements:
- Manufacturing: Final assembly in the United States
- MSRP limits: Varies by your income (see income worksheets)
- Purchase date: Vehicle purchased in 2025
- Primary use: Personal use (not business)
💡 Finding Interest Amount:
Check Form 1098 from your lender, or add up interest from your monthly statements. Make sure to only include 2025 payments, not the full loan amount.
Line 4: Enhanced Senior Standard Deduction
Enter $6,000 for each person (you and/or spouse if filing jointly) who was 65 or older by December 31, 2025. This is in addition to the regular standard deduction.
Age Verification:
- You: Must be 65 by December 31, 2025
- Spouse (MFJ): Each spouse qualifies separately
- Documentation: Birth certificate, Social Security statement, or passport
Example Amounts:
Single, age 67: $6,000
MFJ, both spouses 65+: $12,000
MFJ, one spouse 65+: $6,000
Line 5: Additional SALT Deduction (Over $10,000 Cap)
Enter the amount of state and local taxes you paid in 2025 that exceeds $10,000. You can deduct up to $40,000 total if your MAGI is under $500,000.
SALT Tax Types:
- State income tax: Withholdings + estimated payments
- Local income tax: City or county income taxes
- Property tax: Real estate taxes on your primary home
- State sales tax: Alternative to state income tax (choose higher amount)
📊 Line 5 Calculation:
Total SALT paid: $28,000 • Subtract standard cap: $10,000 • Line 5 amount: $18,000
(This assumes MAGI under $500,000)
Line 6: Total OBBB Adjustments
Add Lines 1 through 5, but apply income phase-outs first if your MAGI exceeds the thresholds. This total transfers to Schedule 1, Line 8l.
⚠️ Don't Forget Phase-Outs!
If your MAGI exceeds $150,000 (single) or $300,000 (MFJ), you must use the phase-out worksheets before adding up your totals. Many people miss this step.
Income Phase-Out Worksheets
Schedule 1-A includes worksheets to calculate reduced deductions if your MAGI exceeds certain thresholds. Here's how they work:
Phase-Out Thresholds
Overtime & Tips
Single: $150,000
MFJ: $300,000
Senior Deduction
Single: $75,000
MFJ: $150,000
Auto Loan Interest
Single: $100,000
MFJ: $200,000
💡 Worksheet Strategy
Complete the worksheets in order: highest MAGI threshold first. This ensures you're applying phase-outs correctly when multiple deductions are affected.
Common Filing Mistakes to Avoid
❌ Critical Errors
- Using total overtime wages instead of premium: Line 1 is only the premium amount
- Forgetting to apply phase-outs: Can trigger audits if deductions seem too high
- Including non-US manufactured vehicles: Must be final-assembled in the US
- Double-counting standard SALT deduction: Line 5 is only the excess over $10,000
- Wrong age calculation: Must be 65 by December 31, 2025, not during 2025
✅ Success Tips
- Keep detailed records: Save all supporting documentation for 7 years
- Double-check W-2 codes: OBBBTT = overtime, OBBBT = tips
- Verify vehicle eligibility: Use the IRS VIN lookup tool for US manufacturing
- Calculate MAGI carefully: Use last year's return as a guide
- Review before submitting: Math errors are the #1 cause of IRS letters
After Completing Schedule 1-A
Once you've filled out Schedule 1-A, you're not done yet. Here's what happens next:
Transfer to Schedule 1
Enter your Line 6 total on Schedule 1 (Additional Income and Adjustments), Line 8l
Complete Schedule 1
Add any other adjustments to income, then total all adjustments
Transfer to Form 1040
Schedule 1 total goes to Form 1040, Line 8, reducing your adjusted gross income
Attach and File
Include Schedule 1-A with your tax return — it's required if you claim any OBBB deductions
Software vs. Paper Filing
As of March 2026, tax software support for Schedule 1-A is still rolling out. Here are your options:
✅ Paper Filing Advantages
- • Available immediately
- • No software bugs or limitations
- • Faster refund processing (file now)
- • Complete control over calculations
- • No additional software costs
🖥️ Software Filing Benefits
- • Automatic calculations
- • Built-in error checking
- • Electronic filing convenience
- • Integration with other forms
- • Support coming mid-March 2026
Get Your Schedule 1-A Numbers Ready
Before you start filling out Schedule 1-A, use our calculator to determine your exact deduction amounts. It handles all the phase-out calculations automatically.