writing off invoices and bills from a closed financial year

I am doing a clean up for a client in reckon hosted
There are a number of bills from suppliers from previous closed financial years that either got paid via other means such as write cheque or just never needed to be paid but were never reversed.
Also some old invoices to customers from previous closed financial years as my client would produce an invoice even if just for a quote (before I told him off) so these old invoices are not actually owing to the client.
How can I clean this up and get them out of the books if the FY is closed off?
Thanks