An unsigned invoice is normal and enforceable. The buyer’s liability comes from the contract and the delivery, and the invoice is the statement of what is owed. Acceptance is shown by the buyer receiving the goods or services, not objecting to the invoice within a reasonable time, claiming input tax credit on it, recording it in their books, or making part payment. Collect that evidence and proceed with a demand, legal notice and, if needed, MSME Samadhaan or a suit.
What an invoice is, legally
An invoice is the supplier’s demand for the price under a contract that already exists. It is not the contract. The contract was formed when the buyer ordered and you agreed; the obligation to pay arose when you delivered. The invoice records the amount, the tax and the terms. Nobody needs to sign a demand for it to be valid. What a court wants to know is whether the goods or services were supplied and accepted, and whether the price claimed is the one agreed.
What proves acceptance instead of a signature
- Receipt of goods or services. Signed challan, POD, e-way bill, or acceptance of the service
- No objection. The buyer received the invoice (email, courier, uploaded to their portal) and said nothing for weeks
- ITC claim. The buyer claimed input tax credit on the invoice in their GST return
- Books. The buyer’s ledger or a balance confirmation showing the invoice
- Part payment. Any payment referencing the invoice
- Messages. “Received your bill, will clear by month end”
Any two of these are usually enough. The ITC claim is especially strong because the buyer has told the government they received your supply.
When a signature does matter
Signatures matter on documents that create obligations or acknowledge them: a contract, a delivery acknowledgement, a balance confirmation, a cheque. If the buyer signed the challan, you have receipt. If they signed a ledger confirmation, you have an acknowledgement that also restarts the 3-year limitation period. If they signed a cheque that bounced, you have Section 138. Focus your file on those signatures, not on the invoice. See no written contract for the wider evidence picture.
The route
Send a written demand attaching the invoice and delivery proof and asking the buyer to confirm the balance. If ignored, FundRaksha’s advocate sends a legal notice within 24 hours that sets out the acceptance evidence and demands payment with interest. India's No.1 B2B payment recovery company, trusted by 1,000+ businesses. Thereafter: MSME Samadhaan for Udyam-registered suppliers (the Council works on invoices and delivery records every day), a summary suit for a liquidated sum, or Section 138 if a cheque was given. See payment recovery.
Make the invoice do more for you
- Print the payment terms, due date and interest clause on every invoice
- Add “Any discrepancy must be reported within 7 days” so silence is clearly acceptance
- State your Udyam registration number if you are an MSME; it alerts the buyer to the 45-day rule and Section 43B(h)
- Send invoices by email as well as with the goods, so receipt is dated
- Ask for a monthly balance confirmation; a signed or emailed confirmation is worth more than any invoice signature
Book a free consultation to have your invoice file reviewed and the recovery started.
Last reviewed: 2026-10-08. Information for Indian businesses; not legal advice.