2. The $306 notice was for "unpaid shared responsibility for 2018", however, I included that in my taxes, in my tax return, therefore, I have already paid for it.
I have tried to contact the IRS, but am unable to do so.
I would appreciate any advice on how to approach this problem?
1) Final amounts for interest/late penalties due can't be assigned until original amount due is fully paid. Thus, two billings is normal under described situation.
2) "Shared Responsibility" implies a second party debt. Filing a joint return? Member of a partnership?