@Sgweiss
There are numerous issues. For one, the IRS has asked that taxpayers wait for guidance.
The APTC, like most things in tax code, isn't as simple as it seems. This part of the tax return mixes in with many other parts of a taxpayer's return. The net premiums paid become part of the calculation of other things, such as a self-employed taxpayer's deduction for self-employed health insurance.
For some taxpayers, this change along with others isn't just "don't pay excess back" but can also mean the taxpayer could be entitled to an additional credit - so someone has to figure that math out and program for it.
The deduction normally taken for health insurance, particularly by the self-employed, which is one of the issues in limbo, also changes the calculations for allowable retirement plan contributions. It affects other taxes on the return. The IRS has not advised how to handle these interdependent areas.
There are dozens of things on the return affected by this issue. It is what it is. Guidance is required.
