Direct answer
A client says the billed work was never done. Defend yourself from the record, not from memory.
The claim lands as one sentence, 'you didn't do this work', and it is built to pull you into an argument you cannot win by talking. Do not take the bait. The defense is a record: what was delivered, when each step ran, and the client's own acceptance with its date, in one place the client can open and check. If that record exists, the conversation is short. This page walks the defense in order, including the version where the record has to be built from what a finished job left behind.
Updated October 29, 2026. First published October 29, 2026.
Step 1. Separate the two claims hiding inside the sentence
'You didn't do the work' means one of two things, and they need different answers. Claim one: the work was never done or never delivered. That is a factual claim, and a delivery record answers it completely. Claim two: work exists, but it is not what was agreed. That is a scope claim, and the agreement answers it, read against the record. Ask one clarifying question if the message is vague, then answer the claim they actually made. Defending against the wrong claim wastes your strongest evidence on a point nobody disputed.
Step 2. Send the delivery record, once, as one link
For claim one, the answer is the record the work left while it ran. When a job runs through Zambo, every call is saved at the moment it runs with a verifiable receipt under AER-1, published as an IETF Internet-Draft (draft-zambo-aer1-26), and the job closes as a handover: goal, steps, outputs, and the client's decision with its date. A real public example of the shape: an accepted handover, 4 of 4 steps checked, decided by the client on 2026-10-16. Send your version of that link. The client can check any receipt free at zambo.dev/verify, no account: the check recomputes the fingerprint over the saved result and compares it with the fingerprint filed when the call ran, so a match shows the saved result was not changed since it was saved.
Step 3. Write the reply in dates, not adjectives
Keep the message short enough that the record does the arguing. The shape that works: the work was delivered on this date, as these deliverables; the record of the job, step by step, is at this link; your acceptance is on it, dated this day; the invoice matches that delivery. Tell me which part of the record you dispute. Four facts and one question. No adjectives about your professionalism, no history of the relationship, no threat. A client with a genuine confusion gets clarity; a client running a payment stall loses the delivery excuse and has to say the quiet part out loud.
Step 4. If the record does not exist yet, build the honest pack
Plenty of good work predates good records. Build the pack from what the job left behind, in this order: the deliverable files with their dates, the thread where the work was sent and received, any acceptance language in the client's own words, then the invoice and the agreement. State what each piece shows and stop there; a pack that overclaims invites the client to attack the overclaim instead of answering the evidence. The general method is on the companion page: how to prove you delivered work to a client. And if the dispute is really about questioned AI work specifically, the dispute kit walks the demand-proof version of this exchange.
Step 5. Make the next job dispute-proof before it starts
Every term of the defense is cheap before the work and expensive after it. Agree up front that delivery closes as a recorded handover with the client's acceptance on it, and that the invoice ties to that acceptance. Then run the job so the record builds itself: on Zambo the free tier is 20 calls + 1 wrap-up free every day, picking up in another AI is always free, a Day Pass at $0.99 is unlimited for 24 hours, and the 153 tools behind the one MCP endpoint each leave a receipt. The next time the sentence arrives, your whole reply is a link.
What a record does not settle
A verifiable receipt proves the saved result was not changed since it was saved; it does not prove the work was good or the answer was right, and it cannot make a client pay. Scope is settled by your agreement, quality by the acceptance, and payment by the terms you both signed. The record's job is to remove the one claim that should never survive contact with evidence: that the work does not exist.
Frequently asked questions
A client claims I didn't do the work I billed for. How do I defend myself?
Answer from the record, not from memory. Separate the claim into its two possible meanings: the work was never done, or the work was done but is not what was agreed. For the first, send the delivery record: the deliverables, the timestamped steps that produced them with a verifiable receipt for each, and the client's acceptance with its date, as one link the client can open and check free. For the second, send the agreement next to the record and walk the scope line by line. One calm message with the record attached settles most of these; arguing in the thread settles none of them.
What evidence should I send first?
Send the strongest single artifact first, not a pile. That is the delivery record with the acceptance on it: what was delivered, when each step ran, and the dated decision where the client took the work. If the job ran through Zambo, that is the handover link, and any receipt on it can be checked at zambo.dev/verify with no account. Follow with the agreement or brief if the dispute is about scope. A pile of screenshots invites an argument about screenshots; one checkable record invites a check, and the check ends it.
What if I did the work before I kept records like this?
Build the best honest pack from what exists: the deliverable files with their dates, the thread where the work was discussed and received, invoices and payment history for the relationship, and any acceptance language, even a 'looks good' in chat. Present it in that order, state plainly what each piece shows, and do not overclaim what it cannot show. Then change the setup for the next job so the record exists before the dispute does: recorded steps, a handover, acceptance on the record.
The client accepted the work and now says it was never done. Does the acceptance settle it?
It is the strongest single fact you can hold. An acceptance on the delivery record, decided by the client with a date, means the client side already confirmed receipt and took the work. A later claim that nothing was delivered has to explain that decision away. Keep the reply short: restate the delivery date and the acceptance date, attach the record, and ask which part of it they dispute. Most of these claims are a payment problem wearing a delivery costume, and the record moves the conversation back to payment, where your agreement governs.