Allocate money in suspense account to open invoice

HI, I rec’d a payment but I didn’t know who this was from so it went to the suspense account.
a month later I now know who paid me and I want to allocate the money in the suspense account to the correct customer invoice,… what is the correct way of doing this?

just edit the transaction in your Bank Transactions or Cash Transactions and select the proper account under the accounts column.
in your case, select Accounts receivable and then select the Customer and click Update.

so I just delete the suspense transaction and receive the payment against the correct invoice ?

you do not have to delete. just edit.

Edit the payment. Set Account as ‘Accounts receivable’, select the Customer, and then you can select the Invoice if you wish (but that is optional). Save the payment with your changes.