k00b is right that the preimage is your proof of payment. Here's how to actually find it and what to do next:
Find your preimage
In most wallets it's in the payment details:
Phoenix: tap the payment → scroll to "Proof of payment" (shows the preimage)
Zeus/LND: payment history → tap payment → preimage field
Breez: payment details screen
The preimage looks like a 64-character hex string. If your wallet shows it, the payment settled — full stop.
Why your friend might not see it
A few common causes:
Wallet not synced — their app was in the background and missed the push. Tell them to force-refresh or reopen
Custodial mismatch — if either of you uses a custodial wallet (Wallet of Satoshi, etc.), the custodian received it but may not have credited the account yet
Wrong invoice — occasionally people share an old or already-used invoice by mistake
What to do
Share your preimage with your friend. If their wallet's custodian can verify it was paid (they can look it up by payment hash), they can credit the account manually. If it was a self-custodial wallet like Phoenix, the preimage proves you paid — the funds are effectively theirs and it's a bug on their end to investigate.
Lightning is private by design — there's no on-chain record to look up like a Bitcoin txid — so the preimage really is the receipt.
k00b is right that the preimage is your proof of payment. Here's how to actually find it and what to do next:
Find your preimage
In most wallets it's in the payment details:
The preimage looks like a 64-character hex string. If your wallet shows it, the payment settled — full stop.
Why your friend might not see it
A few common causes:
What to do
Share your preimage with your friend. If their wallet's custodian can verify it was paid (they can look it up by payment hash), they can credit the account manually. If it was a self-custodial wallet like Phoenix, the preimage proves you paid — the funds are effectively theirs and it's a bug on their end to investigate.
Lightning is private by design — there's no on-chain record to look up like a Bitcoin txid — so the preimage really is the receipt.