If you have been biled with an invoince and later comes a credit note! What are you suppose to do?:o

It usually means the credit note cancels the invoice and you do nothing unless you have paid the invoice and there is is a cheque with the credit note giving you your money back, or in the case of a department store, a credit on your account. Or if you haven't paid the bill, don't pay it.

This depends on whether you've actually recorded the original invoice or not. If you have already recorded it to an expense or asset account and put it into your payables, then you would need to reverse that somehow, and it would depend on how someone wants you to do it.

Definitely you'd need to get it out of the payables. (With a debit.) But what you need to do with the other half of that will depend on what the bill was for, and what the circumstances are. Is this for an actual company, or something that was classroom work? And it would help to know what the invoice was for.