Lightning Invoice

A Lightning invoice is a payment request on the Lightning Network, encoded under the BOLT 11 standard as a long bech32 string that begins with lnbc for mainnet bitcoin. It bundles the amount, a payment hash, the identity of the receiving node, optional routing hints, and an expiry time, which defaults to 3600 seconds in the specification.

Why it matters

Unlike an on-chain address, which can be paid any amount at any time, an invoice is a precise, single-use request. That precision enables point-of-sale commerce: the payer scans a QR code, the wallet decodes the invoice, and settlement completes in seconds. The invoice is signed by the recipient node, so the payer can verify who is being paid before sending anything.

Invoices also produce receipts. Completing the payment reveals a secret preimage that matches the payment hash, giving the payer cryptographic proof that the payment occurred.

How it works

The recipient generates a random preimage and puts its hash in the invoice. The payer routes the payment through hash time-locked contracts keyed to that hash, and every hop in the route can only claim its funds by revealing the preimage, which propagates back to the payer as proof. Because single-use invoices are awkward for tips and recurring payments, newer schemes such as LNURL and BOLT 12 offers build reusable requests on top of the same machinery.