Illinois charges a flat 4.95% and starts from your federal AGI, minus a $2,925 personal exemption per filer. It follows neither the tips nor the overtime deduction, so your Illinois tax is the same whether or not you claim them federally.
What it means on a real paycheck
Take a single filer earning $50,000 a year, $8,000 of it in tips. Against the same person with no tips to declare, the federal deduction is worth $960.
In Illinois it is worth nothing extra. The state bill is identical either way, so $960 is the whole of it.
How Illinois works out the tax
Illinois charges a flat 4.95%, after an exemption of $2,925 a person. It begins from your federal adjusted gross income and applies its own reliefs from there.