My w-2 box 12W reports $8100 as employer contributions to HSA, but the instructions state that employee contributions are to be inclcuded in this number. My portion was $7,100 which I have added to the form 8889 line 2, but Turbo tax won't allow me to adjust the employer portion to their actual $1,000 contribution
for w-2 purposes both your contributions thru your employer and their contributions are included in 12W. your wages, box 1 were reduced by the $7100 that came out of your paychecks. you are not allowed a double benefit. thus it is proper to reflect all the contributions on line 9
and 0 for those contributions on line 2
In most cases, your HSA contribution has already been reported in Box 12 of your W-2 with code W: Employer Contributions to Health Savings Account.
Despite the misleading name, code W reports both your and your employer's contribution. (A better name would be "Contributions to Health Savings Account" but we have no say in the matter.)
So if you put $1,500 in your HSA and your employer matched your contribution, your W-2's Box 12 should have the amount of $3,000 with a code W.
Now, if you made HSA contributions not reported on your W-2 (this is uncommon), we'll ask about that when you step through the Medical section. Look for the questions Were HSA contributions made in 2021? or Do you need to make any adjustments to your HSA contribution amount? Answer Yes and we'll open a screen where you can enter that information.
You only separately enter contributions you made outside payroll, by sending after-tax money directly to the bank.
Under the tax laws, you aren't considered to make payroll contributions. You agree to a salary reduction and the employer makes the contributions, so all the payroll contributions count as employer, both your part and any match.