Unless he was 13 years old or older and you have Child Care Expenses so you can work, indicating he is disabled will have no effect on your tax return.
Do I get a credit or deduction if my child is disabled?
If your child is older than 12 and you need to pay someone to take care of him while you work, you can say he is disabled and you can still get the childcare credit on your federal return. Or if he is 19 or older you may still be able to claim him as a qualifying child dependent on your federal return.
Aside from those things, there is no federal tax advantage to saying that your child is disabled. Your state tax laws might be different.
If you have any medical expenses or have to enroll your child in any sort of special school as a result of his autism, then you may want to enter the medical expenses. They will only have an effect if you meet the very tough threshold to claim medical expenses AND to itemize deductions, though.
MEDICAL EXPENSES
The medical expense deduction has to meet a rather large threshold before it can affect your return. The amount of medical (including dental, vision, etc.) expenses that will count toward itemization is the amount that is OVER 7.5% of your adjusted gross income. You should only enter the amount that you paid in 2022—do not include any amounts that were covered by insurance or that are still outstanding. Of course, your medical expenses plus your other itemized deductions still have to exceed your standard deduction before you will see a difference in your tax due or refund.
To enter your medical expenses go to Federal>Deductions and Credits>Medical>Medical Expenses
2022 STANDARD DEDUCTION AMOUNTS
SINGLE $12,950 (65 or older + $1750)
MARRIED FILING SEPARATELY $12,950 (65 or older + $1750)
MARRIED FILING JOINTLY $25,900 (65 or older + $1400 per spouse)
HEAD OF HOUSEHOLD $19,400 (65 or older +$1750)
Legally Blind + $1750