I agree the that instructions for Form 8889 do not address how to report applying a previous year's excess contribution to the current year. TurboTax has always just added to line 13 the amount present on Form 5329 line 43. However, IRS checking of Form 8889 now appears to expect the excess being applied to be included on line 2, considered to be a contribution for 2023 made on the HSA owner's behalf, in addition to including it on Form 5329 line 43. It's certainly not clear if this was intentional on the part of the IRS or an oversight on their part when adding this math checking to Form 8889.
