I originally created a set of invoices, each with a set of itemised transactions for work done and duly sent them to my client at the time. Because he's tardy, he neglected to pay the invoices on time and they're outside of a 90-day invoice date payment policy, so he's told me to raise new invoices with new dates on them.
I've managed to create credit notes for each quarter for the respective invoices in GNUCash - with credit note 'opened' dated this month - but I'm now wondering how I can duplicate existing transactions used on the old invoices and assign the new transactions to the new invoices? I want to maintain the integrity of the dates and values for existing entries (because of the accounting basis I'm using in the UK), so I can't just raise new current-date invoices with the amounts credited because that would create a false income for the current financial year. I also can't just duplicate the invoices because he's asked that a number of them be combined (because submitting so many at once may cause additional delays in processing them).
Is there a clean way of doing this or do I just have to bite the bullet and manually re-enter the transactions one-by-one on each new invoice?