Be aware that YOU are expected to ensure your orders are certified on or after the first day of duty. Once they are certified, they then go to the RA or equivalent who will eventually get them to finance so that your mil pay can get started. No certified orders passed to mil pay means no mil pay. When you get your paycheck depends on when that duty gets input into the system, there are cutoffs. Even when you get paid, you will have to ensure that you get paid the proper incentive pays (flight pay, etc) and that you are paid the proper BAS (normal BAS on 30+ day orders vs BAH II on shorter orders). Similarly, if your orders are modified to effect mil pay (lengthened, shortened), you are expected to notify the finance people so they can make the appropriate changes. Modifying orders alone does nothing with the mil pay system, the two systems don't talk. Once you start doing UTAs and G/FTPs, the pay gets even more disjointed. My recommendation to you is to get very familiar with the notes section on your LES and use a spreadsheet or some other tracking method to ensure that you are paid for each and every period that you are expecting to be paid.