Sunk costs are expenses you have already paid and cannot get back, no matter what you decide to do next. The idea sounds simple, but it carries real weight in law: contract damages, government contract settlements, and tax deductions all turn on whether a given expense is truly irrecoverable or still within your control. Getting the classification right affects how much you can claim after a breach, what a federal agency owes you if it cancels a contract, and what you can write off when a business asset becomes worthless.
When a Cost Counts as Sunk
Three conditions have to line up. The money has already left your hands. No future decision can bring it back. And no realistic path exists to recoup it through resale, refund, or reuse. If any slice of the spending can still be recovered, only the unrecoverable slice is sunk.
A company that pays $12,000 for market research on a product it later shelves has spent $12,000 that is fully sunk, because custom research has no resale value. A $40,000 delivery van is different. If it can be resold for $25,000, only the $15,000 gap is sunk; the rest is still recoverable through a sale. Employee training works the same way as the research example: $4,500 spent training a worker on proprietary software is gone the moment the session ends, whether or not the worker stays.
Variable costs that rise and fall with what you do next are not sunk, because future choices still control them. Raw materials you have not yet ordered, hourly labor you have not yet scheduled, services you can still cancel — none of these qualify. The dividing line is whether the expense has been permanently disconnected from any choice you still have.
The Sunk Cost Fallacy
The sunk cost fallacy is the pull to keep spending on something because you have already spent so much on it. The past money feels like a reason to push forward, but since it is gone either way, it should carry no weight in the next decision. Only future costs and future benefits are relevant.
Litigation is where this bias does the most damage. A party that has run up $300,000 in legal fees over two years may reject a reasonable settlement because the offer feels too small to “justify” what has already been spent. The reasoning is understandable and financially wrong. The $300,000 is gone whether the case settles today or runs through trial. The only sound question is whether the expected trial outcome, minus the next $200,000 in fees, beats what is on the table now. Cases drag on for years, and costs climb, because that question gets skipped. The guard against it is disciplined review at each stage: will the next dollar meaningfully improve the expected result?
Recovering Sunk Costs After a Broken Contract
When the other side breaks a contract, money you already spent getting ready to perform is sunk — but it is not necessarily lost. Courts can award those preparatory expenses as reliance damages, which aim to put you back in the financial position you held before the contract existed. This is different from expectation damages, which chase the profit you would have made had the deal closed.
Restatement (Second) of Contracts Section 349 gives an injured party the right to recover expenditures made in preparation for performance or during performance. A construction firm that spends $30,000 on site preparation and architectural drawings for a project the developer cancels can seek that $30,000 back, since the drawings and grading work have no use elsewhere. The spending has to have been reasonable and made in genuine reliance on the other party’s promise. Reliance damages are especially useful when expected profits are too speculative to prove, because actual out-of-pocket spending is concrete.
The Mitigation Limit
Recovery has a hard ceiling: once you learn the other side will not perform, you have to take reasonable steps to stop your losses. Costs you keep piling on after that notice are generally not recoverable. In a well-known illustration, a bridge construction company kept building after the county repudiated the contract. The court held that the company had a duty to stop upon learning of the breach and could not recover what it spent afterward. Sunk costs accumulated before the notice are fair game; voluntary spending after it is on you.
When the Federal Government Cancels
Federal agencies can cancel contracts for their own convenience, even when the contractor has done nothing wrong. The Federal Acquisition Regulation sets out a structured settlement process so the contractor is not stuck absorbing every committed expense.
Under the standard termination-for-convenience clause for fixed-price contracts, a contractor can recover:
- Costs of work already performed on the terminated portion, plus initial and preparatory expenses tied to that work.1eCFR. 48 CFR 52.249-2 – Termination for Convenience of the Government (Fixed-Price)
- Costs of settling and paying claims from subcontractors whose work was also terminated.1eCFR. 48 CFR 52.249-2 – Termination for Convenience of the Government (Fixed-Price)
- A fair and reasonable profit on costs already incurred, as determined by the contracting officer. If the contractor would have lost money on the full contract, no profit is allowed and the settlement is reduced to reflect that projected loss.2Acquisition.GOV. FAR 49.202 – Profit
- Accounting, legal, and administrative costs reasonably needed to prepare and negotiate the termination settlement.1eCFR. 48 CFR 52.249-2 – Termination for Convenience of the Government (Fixed-Price)
Costs that continue after the termination date are generally allowable if the contractor made reasonable efforts to shut them down promptly. Costs that linger because of negligence or deliberate inaction are not reimbursable.3eCFR. 48 CFR 31.205-42 – Termination Costs
When Sunk Costs Become Tax Deductions
A business asset that becomes worthless or is abandoned can produce a deductible loss. Under federal tax law, a loss sustained during the taxable year is deductible as long as it is not covered by insurance or other compensation. For individuals, the deduction is limited to losses from a trade or business or from a transaction entered into for profit.4Office of the Law Revision Counsel. 26 USC 165 – Losses
The deductible amount is your adjusted basis in the property, usually what you paid minus any depreciation already claimed. If you paid $85,000 for specialized equipment and took $20,000 in depreciation before abandoning it, your deductible loss would be $65,000, assuming no salvage value and no insurance recovery. Abandonment losses for business property are reported on IRS Form 4797.
Research and development spending follows a different track. Since 2022, businesses can no longer deduct R&D costs in the year they are incurred. These expenditures must be capitalized and amortized over five years for domestic research or fifteen years for foreign research, beginning at the midpoint of the tax year the costs are paid.5Internal Revenue Service. Revenue Procedure 2025-28 The schedule applies whether the research produces a marketable product or ends in a failed prototype.
A Quick Test
Three questions sort most expenses:
- Has the money already been spent? If you can still cancel or avoid it, it is not sunk.
- Can any portion be recovered through resale, refund, or reuse? If so, only the unrecoverable portion is sunk.
- Does any future decision change the loss? If the expense stays the same regardless of what you do next, it is sunk.
Treat the answer as the starting point, not the whole analysis. The legal and tax consequences depend on the context: who caused the loss, when you learned of it, what reasonable steps you took, and what records you kept. The classification tells you what you are dealing with. The rules in contract law, procurement, and tax tell you what you can do about it.