How do I deduct on the return contributions into my HSA not reflected on my W2 because I did a catch up in January to max my allowable 2019 eligible amount.

Did you make this catch-up contribution directly to your HSA outside of your employer?

 

If so, if you told your HSA custodian that the contribution made in 2020 was actually for 2019, then when you go through the HSA interview and see a screen with the heading of "Let's enter [name]'s HSA contribution", include your 2020 amount on the second line ("personal contributions").

 

This field is in essence the total of all contributions made from January 1, 2019 through April 15, 2020 that were made directly to the HSA and not through any payroll deduction.

 

If this catch-up contribution was made through your employer, then come back and tell us so.