I would like to know the references (regulations, etc.) of requiring use of FAR part 15 in awarding IDIQ contracts. I think use of FAR part 15 is useful when we receive offers that include prices that we would like to discuss with the offerors or that have some other factors we need to conduct exchanges. My question is whether we always have to issue RFP and are not allowed to use RFQ using the procedure of FAR part 13? Actually I have seen examples of RFQs to award IDIQ contracts. I would like to know how firm the requirement of using FAR part 15 is. Are there any considerations of the estimated amounts/program amounts and commercial/non-commercials?