For 2019, the maximum allowable HSA contribution is $3,500 for taxpayers covered by an individual (self-only) high-deductible health plan (HDHP) and $7,000 if covered by a family HDHP. This limit increases by $1,000 to $4,500 and $8,000, respectively, if the taxpayer was 55 or older at the end of 2019.
These maximum allowable limits are reduced in certain situations, explained in more detail below. If your 2019 HSA contribution exceeds the allowable amount, the excess must be withdrawn by July 15, 2020 to avoid a penalty (October 15 if you filed an extension).
The $7,000 family limit applies to a married couple if at least one spouse is covered by a family plan. In other words, if one spouse is covered by a family plan, the couple's contribution limit is capped at $7,000 regardless of the other spouse's coverage.
The couple may split their respective contributions any way they like, as long as the couple's total contribution doesn't exceed $7,000. Spouses 55 or older at the end of 2019 may still contribute up to an additional $1,000 to their own HSA.
The maximum allowable HSA contribution is proportionally reduced if the taxpayer didn't have HDHP coverage for the full year and they weren't covered on December 1.
As long as they had HDHP coverage on December 1, they are treated as though they had it the whole year; there is no reduction. Otherwise, the proportion is the number of months they had coverage as of the first of the month, divided by 12. Here are some examples:
Example 1: Taxpayer switches from a self-only HDHP plan to a non-HDHP plan effective August 1, 2019. He had HDHP coverage as of the first of the month from January through July (7 months). His 2019 HSA contribution limit is $3,500 multiplied by 7/12 = $2,042 (rounded).
Example 2: Uninsured taxpayer starts a new job in September of 2019 and signs up for family HDHP coverage through her employer. She is still with the company and hasn't changed insurance. Because she had HDHP coverage on December 1, she can contribute the full $7,000 to her HSA for 2019.
If a taxpayer has other health insurance in addition to their HDHP, such as Medicare, a non-HDHP plan, or a flexible spending account, the taxpayer isn't allowed to contribute to their HSA. More info