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Official form guide
Form 8866: Interest Computation Under the Look-Back Method for Property Depreciated Under the Income Forecast Method
IRS Form 8866 is used to compute interest due or refundable under the look‑back method of section 167(g)(2) for property placed in service after September 13, 1995 and depreciated under the income forecast method, except when the property’s unadjusted basis is $100,000 or less at year‑end.
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IRS Form 8866 - Interest Computation Under the Look-Back Method for Property Depreciated Under the Income Forecast Method
IRS Form 8866 is used to compute interest due or refundable under the look‑back method of section 167(g)(2) for property placed in service after September 13, 1995 and depreciated under the income forecast method, except when the property’s unadjusted basis is $100,000 or less at year‑end.
Risk Radar
Scan points- 1Missing the required signature forfeits the refund and can trigger penalties.
- 2Submitting Form 8866 without the required signature(s), such as missing a spouse’s signature on a joint return.
- 3Mailing a refund‑type Form 8866 to the tax‑return filing address instead of the designated IRS refund address for individuals or other filers.
- 4Leaving lines 9b‑9d blank when you are owed a refund, thereby preventing direct‑deposit of the interest payment.
- 5Filing Form 8866 for property that had an unadjusted basis of $100,000 or less at year‑end, which the look‑back method does not cover.
Plain English
Form 8866 tells the IRS how much interest you owe or should get back for certain depreciable assets like movies or patents. You fill it out for each year you recompute the tax, then send it with your return if you owe interest, or mail it separately if you’re getting a refund.
Submission Date
- Filing date: 2026-01-23 16:10:35
- Preparation window: collect IDs, supporting records, and signatures in advance.
- Final review: verify names, dates, and required fields before submission.
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What this form is for
- Use this form when you need to compute interest due or refundable under the look‑back method of section 167(g)(2) for property placed in service after September 13, 1995 and depreciated under the income forecast method.
- Do not use it when the property’s unadjusted basis (total capitalized cost) was $100,000 or less at the end of the recomputation year.
- Check Form 1040 Schedule 2 instead when you must report interest due on an individual income tax return.
Form selector
Use this form or another form?
Individual with interest due
Interest due must be reported on the individual return line 17n
✓ Verify net interest on line 9a matches the amount entered on Schedule 2
Partnership with interest due
Partnership interest due is reported on line 25 of the partnership return
✓ Confirm the partnership’s EIN and “Form 8866 Interest” appear on any check
S corporation with interest due
Interest due is entered on line 23c as an additional tax
✓ Ensure you write “From Form 8866” on the dotted line left of the entry space
Deadline or filing window
Form 8866 must be filed when you file your income tax return for the recomputation year. The deadline is the same as the return’s due date, and extensions to the return’s filing date also extend the Form 8866 deadline. No separate filing deadline is provided.
Checklist
What you need before filling it out
Line 9a (net interest)
Calculated interest amount · Form 8866
Lines 9b‑9d (direct deposit)
Bank routing, account, and type · Form 8866
Signature section
Taxpayer and preparer signatures · Form 8866
Mailing address for refund
IRS address for individuals or others · Instructions p.2
Recomputation year information
Year and property details · Form 8866 line 1‑5
Before you submit
- 1Verify line 9a contains the correct net interest amount.
- 2Enter direct‑deposit routing, account, and type on lines 9b‑9d if a refund is due.
- 3Complete the Signature section with all required signatures.
- 4Include the correct IRS mailing address for your filer type.
- 5Attach Form 8866 to your tax return when interest is owed; do not attach when a refund is due.
- 6Ensure no more than two prior tax years appear on a single Form 8866 unless additional forms are used.
- 7Sign only the first Form 8866 when filing multiple forms for more than two prior years.
- 8Retain a copy of Form 8866 and any schedules for your records.
How to file this form
- 1Calculate interest using the look‑back method and fill lines 1‑8 on Form 8866.
- 2Enter the net interest on line 9a and, if a refund, provide direct‑deposit details on lines 9b‑9d.
- 3Complete the Signature section, adding both spouses’ signatures for joint returns and the preparer’s signature if applicable.
- 4Attach Form 8866 to your income tax return when interest is owed, or prepare to file it separately when a refund is due.
- 5Mail the completed Form 8866 to the appropriate IRS address (Philadelphia for individuals or Cincinnati for all others) if filing for a refund.
- 6Retain a copy of the form and any attached schedules as proof of filing.
Known limitations
- 1The form does not apply to property with an unadjusted basis of $100,000 or less at year‑end.
- 2The look‑back method is unavailable for property placed in service before September 13, 1995.
- 3Only the taxpayer who had the overpayment may request a refund of interest.
- 4When attaching Form 8866 to a return for interest owed, a signature on the form is not required.
Field map
Compact field-by-field guide
Entity Info
1 items
Name and taxpayer ID of the entity claiming the credit.
Credit Info
1 items
Type of credit or incentive being claimed.
Calculation
2 items
The base amount used to calculate the credit.
Calculated credit amount after applying formulas and limitations.
Certification
1 items
Detailed breakdown supporting the credit calculation.
Signatures
1 items
Sign and date the form.
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Fillable formOpen in Editor->The form is revised December 2025; the instructions direct users to the latest information page at IRS.gov/Form8866.
What changed or needs a fresh check
- Edition date — confirm the revision reads December 2025 (Instructions p.1).
- Fee — Not stated in the official source — verify on the agency site.
- Mailing address — confirm the correct address: Individuals: Department of Treasury, IRS Philadelphia, PA 19255-0001; All others: Department of Treasury, IRS Cincinnati, OH 45999-0001 (Instructions p.2).
- Signature — confirm required signatures: both spouses for joint returns and a paid preparer if used (Instructions p.2).
- Direct deposit fields — confirm lines 9b‑9d are filled when a refund is due (Instructions p.1).
Quick Facts
Downloads
After you file
- 1Keep a copy of Form 8866 and any attached schedules for your records.
- 2If an error is discovered, file a corrected Form 8866 following the correction instructions.
- 3When more than two prior tax years must be shown, file additional Form 8866 copies, signing only the first.
- 4Confirm that filing was completed by the date required for your income tax return, including extensions.
Sources
- SRCInstructions p.1 — revision date is December 2025.
- SRCInstructions p.1 — latest information page: IRS.gov/Form8866.
- SRCInstructions p.1 — purpose: compute interest under look‑back method for property placed in service after September 13, 1995 and depreciated under income forecast method.
- SRCInstructions p.1 — exception: property with unadjusted basis $100,000 or less at year‑end is excluded.
- SRCInstructions p.2 — filing interest owed: attach Form 8866 to tax return; no signature required.
- SRCInstructions p.2 — filing interest refund: file Form 8866 separately; mailing addresses for individuals and others provided.
- SRCInstructions p.2 — signature requirement: both spouses must sign on joint return; paid preparer must also sign.
- SRCInstructions p.2 — additional forms: sign only the first Form 8866 when filing more than two prior tax years.
- SRCInstructions p.2 — filing deadline: file Form 8866 by the date required to file your income tax return (including extensions).
- SRCInstructions p.5 — penalties for not filing or providing false information.
Common confusion points
Do I need to sign Form 8866 when I attach it to my return?
The instructions state a signature is not required for attached forms.
→ Check that you are attaching the form for interest owed; no signature needed.
Should I file Form 8866 with my return or separately?
Interest owed requires attachment; a refund requires separate mailing.
→ Verify whether line 9a shows interest owed (attach) or refund (mail separately).
Which IRS address should I use for mailing?
Different addresses are provided for individuals versus all other filers.
→ Confirm your filer type and use the Philadelphia address for individuals or Cincinnati for others.
Can I report interest due on a partnership using Form 8866?
Partnerships report interest on Form 1065 line 25.
→ Check that the interest amount is entered on Form 1065, not on Form 8866 attached.
Is there a limit on property value for using this form?
The exception applies to property with an unadjusted basis of $100,000 or less.
→ Confirm the property’s unadjusted basis exceeds $100,000 at year‑end.
Do I need a separate Form 8866 for each recomputation year?
The general rule requires filing for each recomputation year.
→ Verify you have a distinct Form 8866 for each year.
Workflow map
Related forms and next steps
Before
Current
After
Often used with
⚠ If something goes wrong
- Form 8866 — file a corrected Form 8866 to amend the interest amount.
Questions about IRS Form 8866
What is IRS Form 8866 used for?
Form 8866 tells the IRS how much interest you owe or should get back for certain depreciable assets like movies or patents. You fill it out for each year you recompute the tax, then send it with your return if you owe interest, or mail it separately if you’re getting a refund.
Who must file IRS Form 8866?
Taxpayers who depreciate property under the income forecast method that was placed in service after September 13, 1995 and had an unadjusted basis over $100,000 at the end of the recomputation year must file Form 8866.
What information does IRS Form 8866 require?
The form collects the calculated interest amount (line 9a) and, when a refund is due, your direct‑deposit details on lines 9b‑9d, along with required signatures.
When is IRS Form 8866 due?
File Form 8866 by the date you are required to file your income tax return, including any extensions.
Where do I file IRS Form 8866?
If interest is owed, attach Form 8866 to your tax return. If a refund is due, mail the form to the IRS address for individuals: Department of Treasury, Internal Revenue Service, Philadelphia, PA 19255‑0001; all other filers send it to: Department of Treasury, Internal Revenue Service, Cincinnati, OH 45999‑0001.
How do I complete IRS Form 8866?
Compute the interest for each prior year and enter the amount on line 9a. If you expect a refund, provide your bank routing, account, and type on lines 9b‑9d. Complete the signature block, signing both spouses if filing jointly, and attach the form to your return when interest is owed or mail it to the appropriate IRS address when a refund is due. Keep a copy for your records.
What happens if IRS Form 8866 is filed incorrectly?
Failing to file, providing incomplete information, or submitting false data can cause loss of any interest refund and may subject you to additional penalties.
Do I need to sign Form 8866 when I attach it to my return?
The instructions state a signature is not required for attached forms. Check that you are attaching the form for interest owed; no signature needed.
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