Form 8889 line 3 not prorating correctly

Forum|Forum|7 days ago
September 9, 2026
3 replies
26 views

Line 3 on Form 8889 shows the maximum HSA contribution for the year based on my coverage and months eligible.

For partial-year coverage, my understanding is that I have to prorate the 2025 maximum based on the months I was an eligible individual with an HDHP. The full 2025 maximum is $4,300 for self-only coverage.

I had HSA coverage only from August 2025 to March 2026 so I’m assuming that Line 3 should show $1792 (August to December 2025). However, it’s displaying $4300. I tried to change it manually, but wasn’t able to. I’m currently using TurboTax desktop version.

How can I correct this?

M-MTax

Level 15

This is what I’ve got:

Since you were covered on December 1, 2025, TurboTax is actually calculating Line 3 correctly according to IRS rules.

Under the IRS Last-Month Rule, being covered on December 1st automatically qualifies you for the full $4,300 annual contribution limit for 2025. TurboTax is legally required to show this full maximum on Line 3 based on your inputs. You cannot manually change this because it is a mandatory tax logic calculation.

Mike9241

Level 15

you are not required to actually use that last month rule. so, you can contribute the prorated amount for months covered in 2025. If you use the LMR to make more than the prorated contribution, you must maintain HDHP coverage in 2026. see IRS PUB 969 for the rules staring on page 6

PUB 969

Mike9241

username4858180Author

Level 2

How would I do this in TurboTax desktop version? There is a section which asks me which months I was covered in 2025 and I selected August – December.