If you moved to Florida and do not intend to return to Illinois, then you would have established residency in Florida and do not need to file an Illinois tax return unless you Illinois sourced income. The fact that you have not changed your driver's license to Florida is just one factor. If you are remaining in Florida, I would go ahead and get a Florida drivers license.
You are an Illinois resident if you were domiciled in Illinois,
but are absent from the state for a temporary or transitory purpose for a period of less than one
year.
An individual is also a resident if he or she is in the state for other than a temporary or
transitory purpose during the taxable year. You are a nonresident of Illinois if you are not a
resident. You are a part-year resident if you became a resident during the tax year or ceased
to be a resident during the tax year.
Residence ceases with the establishment of domicile in another state, which includes a foreign
country.
Illinois Regulations 86 Ill. Adm. Code Section 100.3020(f) provides:
"Presumption of residence and nonresidence. If an individual spends in the aggregate
more than nine months of any taxable year in Illinois, it will be presumed that he is a
resident of Illinois. An individual who is absent from Illinois for one year or more will be presumed to be a nonresident of Illinois.
