Yes, on line 6 of the WI Schedule SB, you would enter amounts deducted for Medicare on your Social Security statement. Here is an excerpt from the form instructions.
You may be able to subtract all or a portion of the cost of your medical care insurance. “Medical care insurance” means a medical care insurance policy that covers you, your spouse, and dependents and provides surgical, medical, hospital, major medical, or other health service coverage (including dental insurance). If you are receiving social security benefits, the amount paid for medical care insurance includes the amount deducted from your monthly benefit for Medicare insurance (for example, Parts B and D)
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I just called the WI Department of Revenue because we had the same double dipping concern. While the rep's rational of "it is done this way to make it easy for seniors to complete their returns" seems odd, Turbo Tax is handling this correctly.
I posed this issue with a former WI Dept. of Revenue employee and this was his response.
Although questionable tax policy, this treatment appears proper. I checked the instructions to the WI Schedule SB and there is no mention of an adjustment in either subtraction for Medicare premiums that are included in the portion of federally taxable Social Security (that is subsequently eliminated from WI income). The WDOR fact sheet on the medical insurance premium deduction doesn’t indicate any reductions or adjustments are necessary.
This outcome is probably due to sloppy drafting of the subtraction modifications. I have seen things like this in other parts of WI tax law. Unless the revenue loss is high, the state puts up with the issue for the sake for keeping its calculations and forms simple.