Divorced in 2018, Healthcare.gov rep advised me to keep my x on the policy and to file taxes jointly. Please advise.

[atb]

Divorced in 2018, Healthcare.gov rep advised me to keep my x on the policy and to file taxes jointly. 

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We divorced in 2018 and were still living together until recently.

I called Healthcare.gov customer service after the divorce was final to ask what to do about our health insurance and do I remove my x-husband from my policy. 

I was the main prescriber and my x-husband was a member. 

The representative told me to keep him on my policy until the end of the year and to file jointly. 

Now that I am preparing our taxes, it looks like I may have been given the wrong information. 

Please advise.

[Opus 17]

You were given incorrect advice.

If you are legally unmarried as of 12/31/18, you must file as single, or head of household if you provided care in your home for a qualifying person (usually a child dependent).  You can't file any version of married.

The share of premiums you paid for someone who is not your tax dependent and not your spouse, is not a deductible medical expense.  For your ex to be your tax dependent for 2018, they would have to have lived in your home for the entire year, and had less than $4150 of taxable income in their own name.