My son goes to school in Texas but when he was home in Alabama for Xmas break last year he purchased a car. This was January 2023. Does he need to file an Alabama return?

[alubu-msn-com]

The tag and sales tax are way less than his standard deduction for federal. But does he need to file anything in Alabama?

[KrisD15]

No, 

If he has no taxable income, there is no reason for him to file. 

Only state INCOME tax withheld is refundable, not sales or property tax you pay.

[Mike9241]

if he had no income there is no return to file

if he did have income, filing depends on the amount and type

Federal

you can check charts B and C in the 1040 instructions

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf 

Alabama instructions

https://www.revenue.alabama.gov/ultraviewer/viewer/basic_viewer/index.html?form=2024/01/23f40bk.pdf 

[Opus 17]

If your son's permanent residence is considered to be Alabama, then he must file an Alabama state income tax return that reports and pays tax on all his world-wide income, regardless of where he was temporarily living or working at the time.  Being "away" at college is usually considered a temporary absence and your son lives at home (as you said).  (To change his permanent address to Texas requires a change of domicile--he must abandon Alabama has his home, move out, change doctors, social relationships, etc. and establish a new permanent residence in Texas that he intends to live in as his permanent home.)

However, you don't mention your son's income.  Just buying a car does not trigger filing a tax return, it depends on how much taxable income he has.