What do I do if a client disputes an invoice after already paying part of it?
Client paid part of the invoice then disputed the rest — what to do
Short answer
Document the partial payment immediately, then respond in writing to the dispute within a few days. Ask for the specific objection — not 'I'm not happy' but 'which line item or deliverable are you disputing and why?' Partial payment is evidence of agreement on the portion paid; the dispute should be limited to the unpaid remainder. If the dispute is not legitimate, the combination of signed work orders, your response documentation, and their own partial payment is strong evidence in small claims court.
A client who pays part of an invoice and then disputes the rest is in a different legal position than one who simply ignores you. The partial payment is generally treated as acknowledgment that at least the paid portion was owed, which narrows any legitimate dispute to the unpaid balance rather than the whole invoice. Document the partial payment with a receipt or confirmation email straight away.
Respond in writing within three to five days of learning about the dispute. Ask the client to be specific: which line item, which deliverable, what they expected versus what they received. A vague "I'm not satisfied" is not an actionable dispute. "The hourly rate was quoted at $X but billed at $Y" is something you can investigate and answer.
Attach your documentation in the response: signed estimate or SOW, any communication where scope or rate was confirmed, completion photos, delivery receipts, or project management records. If the documentation supports the original invoice, say so plainly and set a deadline for the remaining payment. Where the dispute has merit, acknowledge that specific point. Issuing a partial credit note is not an admission that the whole invoice was wrong.
When the client refuses to pay the remainder after a good-faith back-and-forth and you believe the invoice is correct, small claims court is often the right path. Their own partial payment, your signed documentation, and a written dispute response they never substantively countered are usually enough for a judgment. The filing fee is small and you do not need a lawyer. Not legal advice.
Avoid this version of the situation: accepting partial payment silently without documenting what it applies to. If you cash a check with "full and final payment" written on the memo line and don't object, you may have legally accepted it as settlement under accord and satisfaction doctrine. Always respond in writing if you intend to treat a partial payment as partial only, not as settlement of the full balance.