I've got the same issue; we need to be able to import either

a) invoices with a negative quantity & value

-or-

b) credit memos

Can do neither in QBO here in Canada.

I've noted however that the Import Credit Memo functionality does already exist for those using QBO in the UK; which should indicate something fairly easy to provide to others; given the coding already to a large degree exists.

I've noted the responses and, yes, we know a credit memo can be manually entered; however it's a manual process; time consuming when dealing with numerous credit memos that, like invoices and bills could otherwise be imported; and are already being imported by other QBO users..  

Whomever reads this comment; kindly use the gear>feedback to voice your concern to whomever reads them at the other end; hopefully someone hears us and implements this basic function.

Thanks