Form 8697 Instructions for Long-Term Contracts: Look-Back Interest

Form 8697 instructions apply when you complete a long-term contract reported under the percentage-of-completion method and need to settle up interest on the timing differences between the tax you paid using estimates and the tax you would have owed using final numbers. You attach the form to the return for the year the contract wraps, pick one of two calculation methods, run a year-by-year comparison for every prior year the contract spanned, and report a single net interest figure that you either pay to the IRS or receive from it. The form never changes your total tax across the life of the contract. It only prices the time value of money on amounts that were temporarily over- or underpaid.

Who Files and When

You file Form 8697 for each tax year in which you complete a long-term contract entered into after February 28, 1986, that you accounted for using the percentage-of-completion method or the percentage-of-completion capitalized cost method.¹ The computation runs separately for each contract, so three contracts finishing in the same year means three independent look-back calculations.

The form is attached to the return for the completion year and must be filed by that return’s due date, including valid extensions.¹

Partnerships and S-corporations file at the entity level. The entity attaches Form 8697 to its own Form 1065 or Form 1120-S, pays or receives the interest itself, and notifies each partner or shareholder of their share. Individual partners and shareholders do not file separate Forms 8697.

When Look-Back Does Not Apply

Three situations keep a completed contract off Form 8697 entirely. A contract escapes look-back if its final gross price does not exceed the lesser of $1,000,000 or 1 percent of your average annual gross receipts for the three tax years preceding completion, and it was finished within two years of its start date. Both conditions must be met.² Home construction contracts, defined as those where 80 percent or more of estimated total costs relate to building or improving dwelling units in buildings with four or fewer units, are exempt from the percentage-of-completion requirement altogether for regular tax purposes. And you can elect the de minimis exception if your cumulative taxable income under the contract in each prior year was within 10 percent of what the look-back income would have been; this election then applies to every long-term contract you complete going forward unless the IRS consents to revocation.³

What to Gather Before You Start

The calculation is only as reliable as the records behind it. Before opening the form, pull together:

The final actual total contract price and final actual total contract costs at completion. These replace the estimates used in prior years.
The income and deductions you reported under the contract for each prior tax year, as shown on the original returns or any amended versions.
Prior-year tax returns in enough detail to recompute each year’s liability if you are using the Regular Method, or just the income adjustments and highest statutory rates if you are using the simplified method.
IRS quarterly interest rates for every quarter from the due date of each prior year’s return through the filing date of the current year’s return. For 2026, the non-corporate underpayment and overpayment rates are 7 percent for Q1 and 6 percent for Q2; corporate overpayment rates run one percentage point lower.⁴

Choose Your Method: Regular or Simplified

Form 8697 offers two calculation methods, and the choice shapes how much work you do.

The Regular Method, in Part I, recomputes your actual tax liability for each prior year by substituting the final contract figures for the estimates. You need complete tax data for every affected year, including the exact marginal rates that applied. For pass-through entities applying it at the owner level, that means reconstructing each partner’s or shareholder’s individual tax picture for every year the contract spanned.

The Simplified Marginal Impact Method, in Part II, skips the full recomputation. It applies a flat assumed tax rate to the income adjustment: the highest statutory rate in effect for each prior year under Section 1 for individuals or Section 11 for corporations.¹ No year-by-year return reconstruction.

To elect the simplified method, attach a statement to your timely filed return (including extensions) for the first year you want it to apply, stating that you are electing the simplified method under Regulations section 1.460-6(d). The election applies to all future contracts unless the IRS consents to revocation. Pass-through entities that apply look-back at the entity level are required to use the simplified method rather than the regular one.¹

Working Through Part I

Part I handles the Regular Method. Each column represents one prior year in which you reported income from the contract. Six lines carry you through the comparison.

Line 1 is your taxable income or loss for the prior year as originally reported or previously adjusted. Do not reduce this by net operating loss or capital loss carrybacks unless those carrybacks are required to properly compute look-back interest under Section 460.¹

Line 2 is the income adjustment: the difference between the contract income you actually reported (based on estimates) and the income you should have reported (based on final actual figures). A net increase is positive; a net decrease is negative. When figuring the adjustment, account for any other income and expense changes that flow from the contract adjustment.⁵

Line 3 combines Lines 1 and 2 to give adjusted taxable income for look-back purposes. A negative figure represents a look-back net operating loss created or changed by the adjustment.

Line 4 is the hypothetical tax: income tax on the Line 3 amount using the rates actually in effect for that prior year. Reduce it by allowable credits other than refundable credits, do not factor in credit carrybacks, and include any alternative minimum tax that would have applied.¹

Line 5 is the tax liability you actually reported (or that was previously adjusted) for that prior year, computed on the same basis as Line 4.

Line 6 is Line 4 minus Line 5. A positive result means you underpaid tax that year and owe the IRS interest. A negative result means you overpaid and the IRS owes you interest.⁵

Repeat for every prior year the contract spanned. The Line 6 figures become the principal amounts on which look-back interest is calculated.

Computing the Interest

Each prior year’s tax adjustment generates its own interest stream. The accrual period for each runs from the due date of that prior year’s return (ignoring extensions) through the earlier of the due date of the current-year return or the date you actually file it and pay any tax due.¹ A contract spanning five prior years produces five separate interest calculations with five different start dates.

Interest compounds daily, and the applicable rate changes each quarter. Apply the IRS underpayment rate to tax increases and the overpayment rate to tax decreases. Corporate overpayments above $10,000 use a lower rate (the federal short-term rate plus 0.5 percentage points).⁴

Once interest is computed for every prior year, net the total due against the total refundable. That single net figure is the only financial output of the form.

Where the Net Number Goes

How the result appears on your return depends on who is filing:

Individuals filing Form 1040 who owe interest include it in total tax, writing “From Form 8697” and the amount on the line next to the total tax entry.¹
C-corporations report interest due on the schedule used to calculate total tax liability.
Partnerships and S-corporations pay or receive the interest at the entity level and notify owners of their share.

Interest the IRS pays you is taxable interest income in the year you receive or accrue it.⁶ Estimated tax penalties do not apply to look-back interest, but the standard underpayment penalty under Section 6651 can apply if you owe interest and fail to pay.³

Can You Deduct What You Pay

Treatment depends on the taxpayer. C-corporations (other than S-corporations) can deduct look-back interest they pay as interest expense in the year paid or incurred. Individuals and other taxpayers cannot deduct look-back interest at all.¹ The asymmetry for non-corporate taxpayers cuts one way: interest received is taxable, interest paid is not deductible.

Mid-Contract Ownership Changes

If a long-term contract changes hands before completion, the look-back obligation does not simply pass to the new owner. In a constructive completion transaction, the old taxpayer treats the contract as completed in the year of transfer and applies look-back to all pre-transaction years; the new taxpayer is treated as entering a fresh contract and applies look-back only to post-transaction years when the contract actually completes.¹ In a step-in-the-shoes transaction, the new taxpayer inherits the full contract history and, at completion, applies look-back to both pre- and post-transaction years. Regulations sections 1.460-4(g) and 1.460-6(g) govern which category a given transaction falls into.

1
Internal Revenue Service. Instructions for Form 8697 – Interest Computation Under the Look-Back Method for Completed Long-Term Contracts
2
Office of the Law Revision Counsel. 26 US Code 460 – Special Rules for Long-Term Contracts – Section: (b)(3) Special Rules
3
Internal Revenue Service. Examination and Closing Procedures Form 8697, Look-Back Interest
4
Internal Revenue Service. Quarterly Interest Rates
5
Internal Revenue Service. Form 8697 – Interest Computation Under the Look-Back Method for Completed Long-Term Contracts
6
eCFR. 26 CFR 1.460-6 – Look-Back Method