A contractor bills $18,400 for a kitchen remodel, the client pays $4,000 and disappears, and the contractor — on cash basis — claims an $14,400 bad-debt deduction for the unpaid invoice. Next door, a design agency on accrual basis bills $22,000 for a brand package, includes it in income when billed, chases it for nine months with three demand letters and a collections referral, and charges it off in December when the client's LLC is administratively dissolved. The first deduction will be disallowed on audit. The second can survive — but only if the books show the income, the year worthlessness was established, and the business-vs-nonbusiness character was decided at the time the debt was created, not at the time it went bad.
Section 166's bad-debt rules are deceptively short and frequently misapplied by small businesses. An unpaid invoice is not automatically a bad debt; a loan to a friend who runs a business is not automatically a business bad debt; and the year you stop trying to collect is not automatically the year the debt became worthless. This guide explains who can deduct what, how worthlessness and business character are proven, and the bookkeeping that makes a charge-off defensible without a year-end rewrite.
Cash Basis vs. Accrual Basis — The Gate You Can't Skip
Cash-basis taxpayers — which is most small businesses — cannot deduct unpaid receivables as bad debts. The reason is mechanical: a cash-basis business never included the receivable in income, so there is nothing to deduct. The "loss" is foregone income that was never taxed, not a basis you created by parting with money or property. Writing off a $14,400 unpaid invoice where only $4,000 was collected means the business's income was $4,000 — the other $11,400 was never income, so there is nothing to remove.
What a cash-basis business can deduct as a business bad debt is money it actually laid out and is now uncollectible:
- A loan to a customer, supplier, or employee made for business reasons, where basis was cash you advanced and the advance was not income to you
- Advances to contractors or vendors paid but not recovered (e.g., a $7,000 deposit to a subcontractor who never performed and disappeared)
- A guarantee you paid on behalf of the business, creating a right of reimbursement now worthless
Those are true advances of capital that became worthless — deductible if they meet the business-bad-debt tests below. The unpaid invoice is not.
Accrual-basis taxpayers included the receivable in income when the right to receive it became fixed and determinable. When that receivable becomes wholly or partially worthless, Section 166(a) allows a deduction for the worthless portion, but only in the year worthlessness is established, not the year the invoice was issued and not necessarily the year you gave up. The income year and the deduction year are deliberately separate — the system taxes accrual income when earned and relieves it when collection fails, but only on proof.
Constructive or hybrid habits that create errors: depositing a customer's post-dated check as income in the year received (cash rule) vs. when the check becomes payable; booking accrual income for a cash-basis business's "accounts receivable" in project software without ever reporting it; treating an owner's loan to their own S-corp as a bad debt when on audit it is recharacterized as a contribution to capital (no deduction, added stock basis).
Business vs. Nonbusiness Bad Debts — Character Decides Everything
Character is determined by the relationship between the debt and your trade or business at the time the debt was created, not by the fact that you happen to run a business.
Business bad debt — deductible as an ordinary loss, where and when it arises:
- The debt was created or acquired in connection with your trade or business (a customer receivable, a supplier loan to keep product flowing, an employee advance tied to services)
- Or the debt's worthlessness was proximately related to your trade or business — the dominant motive for the loan was business, not investment or personal
Business bad debts are deducted as a business loss — on Schedule C, on the partnership/entity return, or as an ordinary loss where the business reports — and can create or increase a net operating loss. No $3,000 capital-loss limit applies.
Nonbusiness bad debt — the harsher path:
- A loan that is not created in or proximately related to a trade or business — the classic is a loan to a friend or relative, an investment in a startup that is really an equity-like advance, or a shareholder loan that is not business-connected
Nonbusiness bad debts are deductible only as short-term capital losses under Section 166(d), only when wholly worthless (partial worthlessness is not deductible), only in the year they become wholly worthless, and subject to the $3,000 annual capital-loss limit against ordinary income ($1,500 MFS). You must also file a statement attached to the return identifying the debt. A $40,000 nonbusiness loan that becomes worthless yields at most a $3,000 per-year deduction against ordinary income — the rest carries forward as capital loss.
The dominant-motive test — where small-business loans fail. Lending $25,000 to a key customer to keep them afloat has a business motive; lending $25,000 to a brother-in-law's restaurant because you like the concept is personal, even if your day job is consulting for restaurants. The regulations and case law ask: would you have made the loan on the same terms to an unrelated party for the return on the debt itself, or was the business relationship the but-for reason? Mixed motives default to the dominant one, and personal relationships are presumed personal without strong business-purpose documentation created at the time.
Proving Worthlessness — The Most Audited Element
Worthlessness is a facts-and-circumstances determination, and the burden is on the taxpayer. "We stopped calling" is not worthlessness; demonstrable futility is.
Facts that support worthlessness in the year claimed:
- Debtor's financial condition collapses — bankruptcy filing (Chapter 7 liquidation vs. Chapter 11 reorganization matters), assignment for benefit of creditors, administrative dissolution coupled with no assets, judgment proof (no attachable assets after a skip trace), death with insolvent estate, debtor's business permanently closed with no successor
- Collection efforts exhausted — at least two written demands at different addresses, documented phone/email log, referral to a collection agency or attorney with a written "uncollectible" determination, suit considered and declined for documented economic reasons (debtor judgment-proof, amount below litigation threshold — but document the analysis, don't just assert it)
- No payments or promises that would revive collectibility — a partial payment can be evidence the debt is not wholly worthless, since the debtor remains engaged; a written acknowledgment with a payment plan can restart the factual clock
Facts that undercut worthlessness:
- Claiming the debt wholly worthless in the same year invoiced without intervening events — worthlessness rarely arrives that fast except in a bankruptcy filed weeks later
- No written demands, no collection referral, no evidence the debtor's finances were investigated — a verbal "they told me they can't pay" without corroboration
- The debt is between related parties (shareholder and corporation, family) with no arm's-length terms — presumed capital, not debt, until proven otherwise with a note, interest, maturity, collateral, and payment history
Partial vs. whole worthlessness: Business bad debts may be deducted for the partially worthless amount charged off in the year, but only to the extent charged off on the books in that year — the book charge-off is a condition for a partial deduction, not just a habit. Nonbusiness bad debts require wholly worthless before any deduction — charging off part of a nonbusiness loan early wastes the documentation and yields no deduction until the remainder also becomes wholly worthless.
Guarantees: A guarantee is not a debt until you pay it. Only when you honor the guarantee and acquire a right of reimbursement that is then worthless can you claim a bad-debt deduction — and then the worthlessness and business-character tests apply to that reimbursement claim, not to the original guarantee.
The Year Problem — Charge-Off, Specific Charge-Off, and No Reserve
Section 166 small businesses must use the specific charge-off method — deduct the debt when it becomes worthless and charge it off on the books in that year. The reserve method (estimating future bad debts as a percentage of sales or receivables) is allowed only for certain financial institutions — not for contractors, agencies, or retailers. A year-end "allowance for doubtful accounts" entry without identifying the specific debts and why each became worthless in that year is not deductible; it is a book reserve that must be added back for tax.
That means the year of worthlessness is a factual determination you must make and document contemporaneously, not a choice. Relevant markers:
- The first year where all reasonable collection steps have failed and available information shows no reasonable expectation of recovery. A bankruptcy discharge date, a collection agency's written close-out, or an administrative dissolution coupled with a returned demand letter and a negative asset check anchor the year.
- Continuing sporadic payments — even $50 — can push worthlessness into a later year because the debtor is still acknowledging and partially performing
- A debtor who disappears without a forwarding address still requires a documented skip-trace attempt — worthlessness is not assumed from silence alone
Recoveries: If you deducted a bad debt and later collect it (the classic "charge-off then surprise check"), the recovery is income in the year received, limited by the tax benefit rule — to the extent the prior deduction produced a tax benefit. Track recoveries to the original deduction so the lender-borrower-IRS triangle can be reconciled.
Related-Party and Equity Traps
Shareholder/owner loans vs. capital contributions. An advance from a shareholder to their S-corp or LLC without a written note, stated interest, fixed maturity, creditor rights, and repayment history is at risk of being recharacterized as equity on audit or in bankruptcy. An equity contribution has no bad-debt deduction; worthlessness of stock or capital is a capital loss (often limited and long-term). The discipline is boring and decisive: a dated note, market-rate interest, maturity, collateral where appropriate, and actual payments until distress — all created before distress, not reconstructed after.
Personal guarantees of business debt. When an owner guarantees a business's bank loan and the business defaults, the owner's payment creates a debt of the business to the owner. If that debt is worthless because the business has no assets, the owner may have a bad debt — but its character follows the owner's business relationship. A common fact pattern for small-business owners is that the guarantee was business-motivated (to keep the business operating), supporting business character, but the debt is often partially secured or has personal assets of other guarantors that must be pursued before worthlessness can be shown.
Family loans. Document the business purpose with the same rigor as a bank would — use of proceeds tied to the business, business financials at the time, terms a third party would accept — or accept that on audit it will be treated as a gift or equity, not debt.
A Close That Fits Year-End
October–November — the review before the deduction:
- Age every receivable — identify every invoice over 90 days where no payment or payment plan was received, send the second written demand now, and refer borderline accounts to a collection agency for a written collectibility assessment. Accounts without that paper path by year-end cannot credibly be claimed worthless this year.
- Separate advances that are true debts from unpaid invoices that will never be deductible for cash-basis — re-label them in the chart of accounts so a year-end "bad debt" entry doesn't sweep in foregone income that was never at risk.
- For owner and related-party advances, pull the note file — note, interest accrual, maturity, payment history, collateral — and confirm arm's-length terms before year-end, not after.
December — the charge-off decision:
- For each candidate debt, produce a one-page worthlessness memo — debtor identity, amount, date created, business purpose at creation, business vs. nonbusiness determination with dominant-motive explanation, collection log, debtor-financial-status evidence, and the date worthlessness was established. Charge off the specific amount on the books in the same year — the GL entry, the AR subledger removal, and the memo must share a date within the tax year.
- For accrual businesses, the entry is typically
Bad Debt Expense(deductible) /Accounts Receivable — [Debtor]for the wholly or partially worthless amount charged off; for a business loan receivable,Bad Debt Expense/Note Receivable — [Debtor]. For nonbusiness debts, the charge-off must be for the full balance when wholly worthless.
January — the filing package:
- Attach the Section 166 nonbusiness statement where required; keep the worthlessness memo, demand letters, collection-agency determination, and bankruptcy/dissolution evidence with the return workpapers for at least four years (the information and assessment periods around character disputes typically exceed the standard three).
- Book recoveries in the year checks arrive — tie each recovered dollar to the original debt so the tax-benefit-rule limitation can be applied without reconstruction.
The Bookkeeping Connection
Bad-debt deductions reward the habit that makes plain-text accounting powerful: every advance, invoice, demand letter, collection referral, and charge-off is a dated, debtor-tagged event — not a year-end allowance percentage. When the note, the collection log, the worthlessness memo, and the charge-off entry live in the same version-controlled ledger, the story from "$22,000 invoiced, $0 paid, three demands, agency close-out dated November 14, $22,000 charged off December 3" to "accrual Schedule C business bad debt in tax year 2025, 166(a) deduction, memo attached" is traceable and explainable to a preparer who must defend the year worthlessness was established — not the year the receivable was created.
Simplify Your Financial Management
Worthlessness is a factual conclusion with a paper trail and a cutoff date — miss the trail and the deduction is foregone income, miss the date and it belongs in another year. Beancount.io gives you plain-text, version-controlled accounting where notes, receivables by debtor, collection logs, and charge-offs stay explicitly linked — no hidden reserves, no vendor lock-in, and AI-ready when you want help triaging this month's aging into next quarter's determination. Get started for free and make the charge-off match the year it turned.