@kellyr2

The answer provided by @JamesAndrewM is incorrect.  Cash basis taxpayers should not use bad debt expense because you would need to record income to offset the bad debt expense and cash basis taxpayers only record income when payment is received.  If you create a credit memo and apply it, QB will book the income from the invoice and the expense from the credit memo, which you don't want since you never received payment.  That procedure is for accrual basis taxpayers only. 

The proper way for cash basis taxpayers to handle those invoices is to zero them out.