I have a client who earns bi-monthly commission checks that are taxed as supplemental wages in NYS @ 11.7%.  This far exceeds his actual tax rate and he earns most of his money via commission checks.  His wife also works and earns a six figure bonus that is also taxed at 11.7%.  His base pay is about 100K, hers is about 250K.  Combined NYS taxable income is about 1.0M.  Every year they get a large refund back from the state.

In looking at the IT-2104, there doesn't appear to be a mechanism to allow for reduced withholding on their regular pay.  Their respective companies don't allow for anything but the supplemental withholding rate to apply.

Can they claim massive exemptions on their regular wages in order to mitigate what will likely be another year of large overpayments?  What other alternatives are there?

TIA