Pay Stub IDR Calculation

Helping a friend certify income. income fluctuates substantially and is much less now than last year. She has a paystub that is 10 weeks old so within 90 days period. Can she use it for proof of income? She assumes like most years her salary will drop in another month despite this being her busy season. She doesn’t want to use her most recent because it was high due to sales. She understands it will be gross and not AGI but with her deficit this year it makes the most sense. Just confirming if a stub from November will throw a flag and delay processing etc. Thanks