This guide is for individuals, sole proprietors, and pass-through owners who report business activity on Form 1040. That includes Australians and other non-US residents with US filing obligations. "1040 NOL carryback" is shorthand: the claim usually runs through Form 172 plus Form 1045 or Form 1040-X, not Form 1040 alone. Loss year, taxpayer type, and IRS deadlines decide whether you can claim at all. Dollar figures below are USD, since they come from US rules.
Key Takeaways
- An NOL is a tax calculation, not your accounting loss or the loss on your return.
- Most post-2020 individual NOLs carry forward only. Farming losses are the main carryback exception.
- Form 1045 or Form 1040-X is the filing route, depending on facts and deadlines.
- The refund equals the recalculated tax saving, not the NOL amount.
What Is the 1040 NOL Carryback and When Does It Apply?
The basic definition
Under IRC 172, an NOL arises when allowable deductions exceed gross income, after statutory modifications. A raw excess of deductions over income does not automatically create an NOL.
If eligible, the carryback reduces taxable income in an earlier year and creates an overpayment. Any unused or ineligible amount carries forward.
NOL versus other losses
| Loss type | How it differs from an NOL |
|---|---|
| Accounting loss | Tax rules and statutory modifications control, not book results |
| Ordinary business loss | Only an input to the calculation |
| Capital loss | Losses above capital gains cannot create or enlarge an NOL |
The IRS's 2023 Publication 536 shows the gap. A retail owner has a $5,000 business loss, yet after removing nonbusiness items the NOL is only $1,775.
Who can have an NOL
- Sole proprietors, through business losses on Schedule C
- Partners and S corporation shareholders, using their own share of income and deductions
- Estates and trusts, under separate reporting rules
Partnerships and S corporations generally cannot use NOLs themselves. C corporations compute their own NOLs at the corporate level.
Carryback versus carryforward by loss year
| Loss year | Carryback | Carryforward |
|---|---|---|
| Before 2018 | 2 years | 20 years |
| 2018 to 2020 | 5 years under CARES Act, unless waived | Indefinite |
| After 2020 | None for ordinary individual NOLs | Indefinite, generally capped at 80% of taxable income |
Farming losses keep a 2-year carryback, and the election to waive it is irrevocable. Non-life insurance companies have their own 2-year carryback rule.
Historic disaster-loss carrybacks, such as the 5-year rule for disasters before 2010, are not blanket current exceptions. Current section 165(i) lets a qualifying disaster casualty be deducted in the prior year, which is a different election.
Check the loss year against current IRS guidance before you plan anything. Historical rules applied to the wrong year are a common source of rejected claims.
How the 1040 NOL Carryback Refund Process Works
Claiming a 1040 NOL carryback refund follows five steps: calculate the NOL, confirm carryback is allowed, pick the filing route, recompute the prior-year tax, then track whatever remains.
Step 1: Confirm the loss qualifies as an NOL
Start with the loss-year return and complete Form 172 (current revision December 2024). Per the Form 172 instructions, adjust the preliminary loss for:
- Capital losses above includable capital gains
- Nonbusiness deductions above nonbusiness income
- The section 199A deduction
- NOL deductions carried from other years
- Personal exemption-type deductions
Publication 536 stopped with the 2023 edition. Its guidance has moved to the Form 172 instructions, so treat archived examples as illustrations only.
Step 2: Identify the eligible carryback year
Work from the loss year and taxpayer type. Apply the NOL to the earliest eligible year first, then move forward chronologically. Multiple NOLs are used oldest first.
Gather these records before filing:
- Loss-year Form 1040 and schedules
- Business books and income and expense records
- Prior-year returns for the carryback years
- Your NOL computation
- Partnership or S corporation statements (Schedules K-1)
- Evidence supporting any disputed deductions
Step 3: Choose and complete the form
| Route | Deadline | Notes |
|---|---|---|
| Form 1045 (tentative refund) | Generally within 1 year after the loss year ends | File the loss-year return first. E-filing is available under 2025 instructions with Form 8453-TR |
| Form 1040-X (amended return) | 3 years after the loss-year return's due date, including extensions (section 6511(d)(2)) | The ordinary 3-years-from-filing rule does not apply to NOL carrybacks |
The Form 1045 instructions note that Form 1045 cannot carry an NOL to a section 965 year, where an amended return is required. A tentative allowance also does not mean the IRS accepts the claim as correct.
Entering a loss on Form 1040 does not complete a carryback. On the final 2025 forms, an NOL deduction is reported on Schedule 1, line 8a, as a negative figure. That reports a deduction, not a refund claim.
Step 4: Recalculate the earlier-year tax
Recompute the prior year using modified taxable income, not the old return's figure. Taxable income, rates, credits, withholding, and estimated payments all affect the result. An NOL-based refund does not refund self-employment tax.
For example, an NOL of $20,000 applied to a year with $12,000 of taxable income can eliminate that year's income tax, but the refund is capped by tax actually paid. The remaining $8,000 may carry to the next year.
Step 5: Submit, track, and carry the remainder
- Keep proof of filing and all supporting schedules
- Respond promptly to IRS notices
- Reconcile any refund against your computation
- Document the remaining NOL on Form 172 for future years
Processing times vary by route:
- Form 1045: 90-day period starts later than the mailing date
- Form 1040-X: generally 8 to 12 weeks per IRS guidance, sometimes up to 16
- Individual amended returns: averaged over five months in the National Taxpayer Advocate's 2025 report
Plan your cash flow accordingly.
Key Factors That Affect the Refund or Carryforward
Tax-year rules and limits
Label every rule by vintage. Pre-2018 losses can offset up to 100% of taxable income. Post-2017 losses generally face the 80% cap in post-2020 deduction years.
When you hold both, pre-2018 carryovers are used first, and they reduce the base before the 80% calculation.
Computation adjustments
Each modification in Step 1 can shrink or eliminate the loss. Also test the excess business loss limit, which is $313,000 / $626,000 (joint) for 2025 and $256,000 / $512,000 for 2026.
Disallowed excess business losses become NOL carryovers. Losses suspended by basis, at-risk, or passive rules keep their own limits and are not NOLs. Apply limits in this order: basis, at-risk, passive activity, then excess business loss.
Entity and filing-status issues
- Pass-through owners need entity-level information, such as K-1 data, before preparing Form 1040 schedules
- Joint versus separate returns change how the loss and prior-year tax are computed
- Estates and trusts use Form 172 with their own reporting rules
Prior-year tax and refund mechanics
A large NOL against a low-tax year yields a small refund. The refund depends on tax previously paid, credits, withholding, and other deductions. The NOL amount alone tells you little.
Federal versus state, and professional review
A federal result does not decide state treatment. Many states have their own NOL rules.
Get professional review if the claim spans multiple years, involves pass-through entities, international activity, ownership changes, or incomplete records.
Common Issues, Misconceptions, and When Carryback May Not Be Appropriate
Misconceptions
Not every business loss can be carried back, and not every NOL produces a refund. A refund claim has to clear three separate tests:
- A valid loss
- An available NOL
- A permissible refund claim
Frequent filing errors
- Confusing an NOL with a capital-loss carryover
- Applying 2018 to 2020 CARES rules to a post-2020 loss
- Omitting Form 172 or required schedules
- Claiming the loss on the wrong return
- Missing the Form 1045 or 1040-X deadline
Incomplete lines or missing forms can delay or disallow a Form 1045 application.
When carryback is the wrong tool
- Little taxable income in the earlier years
- No way to substantiate the loss
- Stronger income ahead, so a carryforward is worth more
- A limitation caps the benefit
If you need help reviewing NOL records, preparing supporting calculations, or coordinating multi-year filings, VJM Global provides tax compliance and accounting support through US-compliant professionals.
VJM Global also prepares US individual returns, including Form 1040 and 1040-NR. Eligibility and refund amounts depend on your facts, and no outcome can be promised in advance.
Conclusion
Claiming an NOL refund takes more than a negative business result. You calculate the tax NOL, confirm carryback eligibility for the loss year, use the correct IRS procedure, and meet the deadline.
Rules differ by loss year, taxpayer type, and exception, so keep clean records and check current IRS guidance. Compare carryback and carryforward value before you file.
Frequently Asked Questions
Where do I report a NOL carryover on 1040?
The deductible amount generally goes on Schedule 1, line 8a (2025 form), as a negative figure, flowing to Form 1040. Line numbers change, so check the current Form 172 and 1040 instructions.
What form shows NOL carryforward?
Form 172 computes the NOL and the remaining carryover. Amended-return or Form 1045 filings rely on it, and the 1040-X instructions still reference former Form 1045 schedules.
What are the rules for carrying forward IRS NOLs?
Post-2017 NOLs carry forward indefinitely, generally limited to 80% of taxable income in post-2020 years. Pre-2018 losses go first, and multiple NOLs are used oldest first. Confirm exceptions for your loss year.
How long can a taxpayer carry forward a net operating loss?
Post-2017 individual NOLs carry forward indefinitely. Pre-2018 NOLs carry forward 20 years. Non-life insurers have separate rules, so confirm the tax year.
Can I carryback a NOL?
Generally not for post-2020 ordinary individual NOLs. Farming losses carry back 2 years, and 2018 to 2020 losses had a 5-year carryback under the CARES Act.
What is a business loss carryover?
It is a loss suspended by basis, at-risk, or passive rules, which keeps those limits when used later. It differs from an NOL, except that disallowed section 461(l) excess business losses become NOL carryovers.
