Can we make use of AWS Credits to Purchase the reserved instances?

In this case the solution could be to purchase RIs or Savings Plans with the No Upfront payment option. With this payment option, you get monthly charges for the RI/SP subscription, which are included in your regular monthly bill, which can be covered by Credits. However, I highly recommend to check which services are covered by your Credits. Because, for example, if you got Credits to cover certain AWS services, which don't have RI model, or if your Credits don't specify that they can cover Savings Plans, then even if you buy No Upfront RIs or SP, you may not get covered. If you're not sure - you can open a support case from your account, and our support team should be able to help you to find out which services can be covered by your credits.

Does RDS RIs no upfront monthly bill can be paid using credits