Commission arguments usually are not about money. They are about trust: a stylist who cannot reconstruct their own month will assume the number is wrong, even when it is right. The fix is to make commission visible at the line where the sale was rung up.
Decide your basis once and hold it. A percentage per service is the cleanest when your menu has very different prices, because a braiding session and a beard trim should not earn the same absolute amount. A single salon-wide percentage is easier to explain when prices are close together. Either way, store the percentage and record the amount that was actually paid on the sale line, so a later rate change never rewrites history.
Give each staff member their own desk. When a stylist opens the POS and sees their commission for the month, the sales that produced it, and the payments already made to them, month-end becomes a signature instead of a negotiation. Managers keep the full picture; staff see their own.
Handle advances before payday, not during it. An advance approved mid-month should be booked as an expense of type ADVANCE and netted off the salary automatically. Recording it in a notebook, or as a generic expense, is how month-end disputes start.
Finally, keep the base salary and commission visibly separate in the payslip. Staff forgive a slow month; they rarely forgive a number they were never allowed to see broken down.