A C corporation that loses money in one year can use that loss to reduce taxable income in future profitable years by claiming a net operating loss deduction on Form 1120. Under the carryforward rules in effect today, losses generated in tax years beginning after December 31, 2017, carry forward indefinitely but can only offset up to 80% of taxable income in any single year. Older losses follow a different set of rules, and any corporation that has changed hands faces an additional annual ceiling under Section 382.
Figuring the Loss in the First Place
Section 172 defines a net operating loss as the amount by which allowable deductions exceed gross income for the year, with certain adjustments.1Office of the Law Revision Counsel. 26 U.S. Code 172 – Net Operating Loss Deduction For a C corporation, the calculation starts with the taxable income or loss figure already on Form 1120 and applies two modifications.
First, a prior year’s NOL cannot be deducted when computing the current year’s NOL. Without this rule, old losses could stack on top of new losses and inflate the carryforward. Second, the dividends received deduction is recalculated without the usual taxable income cap. Normally, a corporation owning less than 20% of another company can deduct 50% of dividends received, capped at 50% of taxable income; the 65% deduction for corporations owning 20% or more works the same way. When computing the NOL, that taxable income cap drops away and the full deduction is allowed.2Office of the Law Revision Counsel. 26 U.S. Code 172 – Net Operating Loss Deduction – Section: Modifications Most other Section 172(d) modifications apply only to individuals and can be ignored on Form 1120.
How Long the Loss Carries Forward
The Tax Cuts and Jobs Act split NOLs into two eras. Losses from tax years beginning before January 1, 2018, carry forward 20 years from the loss year. Losses from tax years beginning after December 31, 2017, carry forward indefinitely with no expiration.3Office of the Law Revision Counsel. 26 U.S. Code 172 – Net Operating Loss Deduction – Section: Net Operating Loss Carrybacks and Carryovers The TCJA also eliminated the two-year carryback that previously let corporations amend prior returns for a refund.4Congressional Research Service. Tax Treatment of Net Operating Losses in the CARES Act
A temporary CARES Act exception allowed losses generated in 2018, 2019, and 2020 to be carried back five years using Form 1139 for an expedited refund.5Internal Revenue Service. Frequently Asked Questions About Carrybacks of NOLs for Taxpayers Who Have Had Section 965 Inclusions That window has closed. Any loss generated after 2020 must be carried forward only.
A corporation can therefore be sitting on NOLs from more than one era, each following its own rules. A pre-2018 loss has a 20-year shelf life but no percentage cap on use. A 2018–2020 loss may already have been carried back. A post-2020 loss carries forward forever but runs into the 80% ceiling. Tracking each vintage separately is not optional, because the applicable limitation depends entirely on when the loss arose.
The 80% Taxable Income Limit
For tax years beginning after December 31, 2020, the NOL deduction follows a two-tier formula. Pre-2018 losses go first and can offset 100% of taxable income with no percentage cap.6Internal Revenue Service. Instructions for Form 172 – Net Operating Losses for Individuals, Estates, and Trusts Post-2017 losses come second and can offset only 80% of whatever taxable income remains after the pre-2018 losses are absorbed.7Office of the Law Revision Counsel. 26 U.S. Code 172 – Net Operating Loss Deduction – Section: Deduction Allowed The 80% figure is computed on taxable income before deductions under Sections 172, 199A, and 250.
Here is how the math works. Say a corporation has $200,000 in pre-2018 carryforward and $3,000,000 in post-2020 carryforward, and it earns $1,000,000 in taxable income this year. The $200,000 pre-2018 loss offsets the first $200,000, leaving $800,000. The post-2017 cap is 80% of that $800,000, which equals $640,000. Total deduction: $840,000. The corporation pays tax on the remaining $160,000 and carries $2,360,000 in post-2020 losses to next year.
Take away the pre-2018 losses and the entire $1,000,000 faces the 80% cap. Maximum deduction: $800,000. Taxable income: $200,000. At the 21% corporate rate, that produces a $42,000 tax bill even with millions in accumulated losses. The unused portion carries forward indefinitely, but a corporation with large carryforwards and steady profits will take years to burn through them.
Reporting the Deduction on Form 1120
The NOL deduction goes on Line 29a of Form 1120, labeled “Net operating loss deduction.”8Internal Revenue Service. Form 1120 – U.S. Corporation Income Tax Return The amount entered cannot exceed taxable income after special deductions, and you must attach a statement showing how the deduction was computed.9Internal Revenue Service. Instructions for Form 1120
The IRS does not prescribe a rigid format for that statement, but it has to function as a running ledger. For each loss year, show the original NOL amount, the cumulative amount used in prior years, the amount applied in the current year, and the remaining balance. When the corporation holds losses from multiple vintage years, the statement must track each one separately, because pre-2018 and post-2017 losses follow different utilization rules.
This statement is where most compliance problems surface. A corporation that fails to segregate loss vintages, or that applies the 80% limit to pre-2018 losses when no cap applies, will either overpay or face an adjustment on audit. The Line 29a figure flows directly into taxable income, estimated payment calculations, and any financial statement provisions.
One Point on Charitable Contributions
The corporate charitable contribution deduction is capped at 10% of taxable income, but that taxable income figure is calculated before subtracting any NOL carryback, the charitable deduction itself, the dividends received deduction, or any capital loss carryback.10Office of the Law Revision Counsel. 26 USC 170 – Charitable, Etc., Contributions and Gifts A large NOL carryforward applied to the current year does not shrink the 10% base.
Section 382: The Cap After an Ownership Change
When a corporation with accumulated losses changes hands, Section 382 caps how quickly the new owners can use those losses. The rule exists to prevent profitable companies from buying loss-heavy shells for the deductions.
An ownership change occurs when one or more 5-percent shareholders increase their combined ownership by more than 50 percentage points over a three-year testing period.11Office of the Law Revision Counsel. 26 USC 382 – Limitation on Net Operating Loss Carryforwards and Certain Built-In Losses Following Ownership Change A single acquisition can trigger it. So can a series of smaller transactions that collectively cross the threshold.
Once an ownership change occurs, the corporation faces an annual ceiling on pre-change NOL usage equal to the fair market value of the loss corporation’s stock immediately before the change, multiplied by the IRS-published long-term tax-exempt rate. As of early 2026, that rate is 3.58%.12Internal Revenue Service. Rev. Rul. 2026-6 If a loss corporation was valued at $50 million just before the change, the annual cap is $1,790,000. Even with $20 million in accumulated losses, only $1,790,000 can be used per year until the losses are exhausted or expire.
The Section 382 ceiling applies to the pool of available pre-change NOLs before the 80% taxable income limit takes its cut. If the Section 382 cap is lower than 80% of taxable income, the Section 382 cap controls. Any pre-change losses blocked by the annual ceiling carry forward to the next year, and unused limitation amounts can sometimes increase the following year’s cap. Run this analysis before closing any merger, acquisition, or significant equity restructuring; overlooking Section 382 can turn a valuable tax asset on the balance sheet into something worth far less in present-value terms.
State Returns Do Not Automatically Follow
Federal NOL rules do not flow through to state corporate income tax returns automatically. Many states impose their own carryforward limits, often 12 to 20 years rather than indefinite. Some states follow the federal 80% cap, others allow full offset, and a few have suspended NOL deductions during budget shortfalls and later restored them. If your corporation files in multiple states, each state’s return needs its own NOL tracking schedule, and the balance of available losses will diverge from the federal figure over time.