You will need to mail in the return for 2021 due to the unusual circumstance of having to file single, but including an ex-spouse income/withholding.
You will enter the income that belongs to you according to the laws of WI as if earned by you. For example, if your W2 has a box 1 amount of 10,000 that is all yours but you must include 50% of your ex-spouse's W2 income, you would enter you spouse's W2 with your social security number and change the box 1 amount in those W2 entries to what it is legally supposed to be for you. You would do the same for box 2 (withholding) and box 16 and box 17 (state boxes). Leave the other boxes for her W2 blank.
If part of your W2 belongs to your spouse change the box 1, 2, 16 and 17 as needed.
You use the same method (enter as if you earned it) for any income source or deduction from your ex-spouse.
Next you will need to complete a form 8958 to show the allocations on your return. If you are using a TurboTax desktop product you can use the "Forms View" and search for the "8958." You can type into the form. Check the box indicating you have allocated on your return. Complete the columns for each item that was altered/allocated in your return.
You can print the form separately for mailing in with your other completed tax forms for mailing. The form will not normally print as part of a return that is not Married Filing Separate. You might also include a copy of the page of your divorce decree that directs the allocation.
If you are using an online product, download/complete the form from the IRS site and print it to include with your other completed tax forms for mailing. You might also include a copy of the page of your divorce decree that directs the allocation.
Be sure to keep records of how you allocated each item.
Edited [3/14/2022 9:54 PDT]
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