Hello Campersteve, thank you for contacting the Community. We apologise for the delay in replying.
In order to use a credit for a later invoice you would need to turn of the auto apply credits option in the settings of QuickBooks. To do this go to the cog in the top right of QuickBooks> account and settings>advanced>auto apply credits>toggle off and then save and then click on done.
Once you have done that you can add your customer credit note as normal. It will then stay on that customer and when you wish to use it go to receive payment on the invoice you wish to allocate it to and then put a tick in the credit you will see as an option to pay or part pay the bill.
Any questions please let us know.
