To hide overdue rent invoices that have been written off, go to Accounts, then navigate to General and select Credit Note. Allocate the credit note to the overdue rent invoice to remove it from the outstanding list. Be sure to add a description such as "Written-Off Arrears" to clarify the reason for the credit. Please note that the invoice and credit will still appear on the accounting and landlord statements unless they are specifically excluded. This same process can also be used to credit a tenant for an expense they have paid for themselves, such as a replacement toaster.
Further Reading: Updating Next Rent Due Date In iamproperty CRM