If you make contributions via payroll, you gain an additional 7.65% tax savings because the HSA deduction is taken out before social security and medicare tax. If you pay yourself, you get the income tax savings but not the payroll tax savings.
So if you, for example, contribute $2000 now and then $116 per month, you would be giving up $153 in additional tax savings.
If you are trying to build up your account for a large bill early in the year, note two things.
1. If you did not max out your contribution for 2017, you can make a contribution up until April 15, 2018, and have it treated as a 2017 contribution. You get the tax savings on your 2017 tax return and you still have a full limit for 2018. Be sure to tell the trustee this is a prior year contribution.
2. If you have a large bill early in the year and not enough to cover it, you can pay out of pocket and then reimburse yourself at the end of the year once your account fills up.
