The last month rule allows an eligible person to contribute
up to the maximum contribution limit to their Health Savings Account (HSA) if
they are covered by a High Deductible Health Plan (HDHP) on December 1st
of a tax year. The “catch” for being
allowed to contribute so much to the HSA is that they must remain enrolled in
the HDHP through the entire following year or there will be tax
consequences.
In your case, since you remained enrolled in a HDHP for the entire year of 2016 (even though it was
with two different plans), the last
month rule would not apply. For it
to apply, you would have had to contribute more than your ordinary monthly
amount to the HSA in December of 2015
and you would have had to break your
coverage in a HDHP at some point during 2016.
