Use take-home pay
Budget with the amount that reaches your bank account after taxes, insurance and retirement deductions, not your salary. That's the money you can actually spend.
If your income changes
Freelancers, tipped workers and anyone with variable hours should budget on their lowest normal month from the past year. Anything above that is a bonus that goes to savings or debt.
Count every source
Add side income, child support, benefits and regular transfers. Leave out one-off money like tax refunds; plan those separately.
Do this today
Write down your monthly take-home pay from your last three pay stubs or deposits, and circle the lowest month.