Mortgage Credit Certificate

[Salley Smith]

I have a house which I bought with my co- borrower in 2016, and we pay about 600 dollars of interest monthly. I paid a downpayment of 10,000 this year (no points) when we bought the house, and have spent 10,000 dollars on renovation costs. We both make 32,000 dollars yearly, and are not currently married.  I have a mortgage credit certificate, which I believe was issued jointly.  I am trying to figure out if I can file taxes as single or if it makes more sense/ is necessary to file them jointly.  If we file jointly, the penalty for not having Obamacare will be around 700 dollars more. Please advise. Thank you for your time.