If a client’s charge was missed, you have two options to correct it.
By default, the missed charge will automatically be added to the next billing cycle. Alternatively, you can backdate and reissue the invoice so the payment is processed immediately.
To backdate and reissue an invoice
Go to the Invoices page and find the relevant invoice
Click on the […] and choose Send now
Choose what date you want to backdate the invoice
Click Send invoice now
Please be aware that if you've locked your ledger, you won't be able to create invoices in Xero. You will need to unlock the previous month first, and then run this process.