To contribute the maximum amount to your HSA, you must have been enrolled in an eligible HDHP and had no other disqualifying insurance for all the months of 2022, or, you were eligible in December 2022 and are going to use the last month rule, which requires that you remain eligible for all of 2023.
Yes, you can top off your HSA up until April 15, 2023, and have it counted for 2022. Make sure you inform the HSA bank in advance, if you contribute electronically, make sure you select 2022 on the contribution form.
If you also had payroll deductions to your HSA, remember that TurboTax will automatically fill that in from your W-2. Later in the program when you are asked about separate HSA contributions, only enter your own direct contributions not through payroll. If you enter your payroll deductions twice, TurboTax will think you over contributed and will assess a penalty.
