IFTA per quarter question for owner operator/carrier with few trucks

When a driver quits it is best to hold their pay until you check their equipment and make sure you have all their paperwork. No paperwork, no paycheck. I have all drivers sign a contract. I put in black and white how and when they will be paid and unless I have ALL paperwork by a certain date, they don't get paid. Most of the time it helps to get the paperwork in a timely manner. They understand that I need the paperwork to calculate their pay. I also need the bills to get my money.

I rarely spend over $25-75/quarter. I figure my mileage the way they want and it usually comes out over 5 mpg. I did get over 7 in one quarter. It is difficult to get out of the 5's the way they want you to calculate the mpg.