There are multiple words which can be used as synonyms for "not paid for." Some of the possible options include: outstanding, unpaid, unsettled, uncollected, overdue, delinquent, and owing. The use of any of these words can accurately convey the meaning that a payment has not been made or received. Depending on the context, some synonyms may be more appropriate than others. For example, an invoice might be referred to as "unpaid" or "outstanding" while a debt might be described as "delinquent" or "owing." Regardless of the choice of synonym, it is important to use clear language when discussing financial matters.