It may not be worth the 'fight' for just one year of insurance, but the definition of "dependent" for issuing health insurance is not the same as a Tax Dependent. For issuing health insurance, "dependent" only has to do with the relationship. For tax purposes, "dependent" as far more restrictions (living with you, support, etc.).
Here is the legal gibberish:
A group health plan, or a health insurance issuer offering
group or individual health insurance coverage, that makes available dependent
coverage of children must make such coverage available for children until
attainment of 26 years of age.
Restrictions on plan definition of dependent - In general. With respect to a child who has not attained age
26, a plan or issuer
may not define
dependent for purposes of eligibility for dependent coverage of children
other
than in terms of a relationship between a child and the participant
(in
the individual market, the primary subscriber). Thus, for example, a plan or
issuer
may not deny
or restrict
dependent coverage for a child who has not attained age 26 based on the
presence or absence of the child's financial dependency (upon the participant
or primary subscriber, or any other person); residency with the participant (in
the individual market, the primary subscriber) or with any other person;
whether the child lives, works, or resides in an HMO's service area or other
network service area; marital status; student status; employment; eligibility
for other coverage; or any combination of those factors. (Other requirements of
Federal or State law, including section 609 of ERISA or section 1908 of the
Social Security Act, may require coverage of certain children.)
https://www.law.cornell.edu/cfr/text/45/147.120
https://www.law.cornell.edu/cfr/text/29/2590.715-2714
At any rate, it does NOT affect your eligibility for the Premium Tax Credit.
