@Charm25 

You can zero out the invoices if you have access to make changes to prior, closed periods.  Since you're on cash basis, those entries were never on your balance sheet or P&L so zeroing them out will not impact any cash basis closed period.  It will affect any prior period accrual basis reports.    

If you don't have access to make changes, then, IMO, you should create credit memos that offset the revenue on the invoices, not create an offsetting expense.  On cash basis, when you apply a credit memo to an invoice, QB increases your revenue based on the invoice amounts and then offsets that with whatever accounts are assigned to the Product/Services on the credit memo.  If you assign an expense account to the credit memo, your revenue and expense will both increase, thereby offsetting.  That's correct for accrual basis but not cash.  On cash basis, you don't increase revenue, so the Product/Service on the credit memo should match the income accounts associated with the invoices.  That why it's easier to just zero out the invoices IMO.  Forgive me if you know all of this already.