Why is the invoice I'm trying to allocate a payment to greyed out?

Typically, invoice payments are received after an invoice has been issued i.e. the date an invoice payment is received will be after the invoice date.

If you create accounts on an accruals basis, and the date an invoice payment is received is before the invoice date:

(1) you will not be able to match the invoice payment (the confirm button is hidden)

(2) and the invoices will be greyed out within the Enter New Transactions popup.

To fix this you will need to either:

1. Update the invoice date to before the date that the payment was received.

2. Record the income as 'Income Recieved' against your intended income category, and then within the invoicing module create a credit note from that category, for the relevant customer. You can then reconcile the credit note against the invoice within the invoicing module.