How to file a tax extension in 2025: Step-by-step instructions
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How to file a tax extension in 2025: Step-by-step instructions
With time until Tax Day running short, explains how to submit a six-month federal filing extension in four simple steps, followed by advice on state tax extensions and navigating the tax-filing implications of complex financial situations.
Federal Tax Extension Process
Step 1: Prepare Form 4868
is the "Application for Automatic Extension of Time to File U.S. Individual Income Tax Return." This form extends your filing deadline to Oct. 15, 2025.
Step 2: Calculate Your Estimated Tax Liability
You must pay any taxes owed by April 15, 2025, to avoid penalties and interest.
- Gather your financial documents:
- Income documents (W-2s, 1099s, K-1s)
- RSU vesting statements and option exercise documents
- Investment statements showing capital gains/losses
- Rental property income and expense records
- Business income and expense documentation
- Deduction records (mortgage interest, charitable contributions)
Get your full checklist .
- Calculate your estimated federal tax:
- Start with your total income (wages, RSU income, business income)
- Add investment income (dividends, capital gains)
- Subtract adjustments to income (retirement contributions, HSA)
- Subtract standard or itemized deductions
- Calculate tax based on your tax bracket
- Add any alternative minimum tax (AMT) if applicable
- Subtract credits you qualify for
- Subtract federal income tax already withheld
- Subtract estimated tax payments already made
- For equity compensation:
- RSUs: Account for taxes already withheld at vesting (typically 22%-37%)
- NSOs: Calculate the bargain element (market price minus strike price)
- ISOs: Consider potential AMT implications
You can learn more about how equity is taxed .
- For capital gains:
- Separate short-term (held < 1 year) from long-term (held > 1 year) gains
- Apply appropriate tax rates (ordinary income for short-term; 0%, 15%, or 20% for long-term)
- Include 3.8% net investment income tax if your income exceeds thresholds
Step 3: File Your Extension Request
Choose one of these filing methods:
- Electronic filing through tax software
- IRS Free File on the IRS website
- Mail a paper form to the IRS address listed on Form 4868
The extension must be submitted by April 15, 2025.
Step 4: Pay Your Estimated Tax
Even with an extension, payment is due April 15, 2025. Payment options include:
- IRS Direct Pay: Pay directly from your bank account
- Electronic Federal Tax Payment System (EFTPS): Requires enrollment
- Credit/debit card: Fees apply
- Payment with extension form: Include payment when filing Form 4868
- Check or money order: Send with a payment voucher
State Tax Extension Process
Step 1: Determine Your State Requirements
State extension requirements vary:
- Automatic extension states: Many states automatically grant an extension if you receive a federal extension
- Separate filing states: Some states require their own extension forms
Step 2: File State-Specific Extension Forms (If Required)
Common state-specific forms include:
- California: Form FTB 3519
- New York: Form IT-370
- New Jersey: Form NJ-630
Step 3: Calculate and Pay Estimated State Taxes
For your resident state:
- Calculate tax on all income following state-specific rules
- Subtract state taxes already withheld
- Pay estimated amount due by your state's deadline
For nonresident states:
- Calculate tax on income sourced only to those states
- File extensions for each applicable state
- Pay estimated taxes owed to each state
Multistate Considerations
If you have income across multiple states:
- Determine your state of legal residence/domicile
- Identify which states have taxation rights to different income sources
- Calculate credit for taxes paid to other states
- Review any reciprocity agreements between states
- File separate extensions for each state where required
For Complex Financial Situations
Real Estate Investments
For properties owned across multiple states:
- Calculate net income or loss for each property
- Track passive activity limitations
- Allocate expenses properly between states
- Consider depreciation recapture if properties were sold
For a full guide on the tax advantages of real estate, read more .
Stock Options and RSUs
- Maintain detailed records of grant dates, vesting dates, exercise dates, and sales
- For ISOs, track holding periods to determine tax treatment
- For disqualifying dispositions, calculate additional ordinary income
After Filing Your Extension
- Receive confirmation of extension filing (keep for your records)
- Continue gathering necessary documentation for your complete return
- Work with your tax professional to complete returns
- File your complete tax returns by Oct. 15, 2025
Important Reminders
- An extension gives you more time to file, not more time to pay
- Payments made after April 15, 2025, will incur penalties and interest
- The late payment penalty is 0.5% of unpaid taxes per month (up to 25%)
- Interest charges apply at the federal short-term rate plus 3% (compounded daily)
- Filing an extension eliminates the more severe 5% per month late filing penalty
- When estimating taxes due, it's better to slightly overpay than underpay
- If you're ready to make your estimated payment, go to .
Following these steps will help ensure you properly extend your tax filing deadline while avoiding unnecessary penalties and interest charges.