You are quite mistaken ... the 1095-A shows the amount paid for insurance for the year it is issued EVEN if you pay the Jan premium in December ... this is allowed and how it has been for the last 6 years ... it is SOP and neither I nor any of my clients have gotten a letter from the IRS about it.
I see your position ... say in Dec 2018 your only payment is for the Jan 2019 ACA insurance and you only make 11 payments in 2019 if you did not renew the ACA insurance for 2020. What you want the ACA to do is issue a 2019 form 1095-A with the one payment on it and a 2019 form with the rest. This is not the case ... they have always made it simple by putting it all on the tax year the insurance covers and not when you make the payment .... and this is not going to change.
