Despite the fact that your spouse is disabled and is receiving SS benefits, she is receiving taxable income, so you might want to re-think changing your W-4. There is no place to say that your spouse is disabled on a W-4. If you file a joint return then all of your combined income must be entered on it including your spouse's SS income.
https://www.irs.gov/pub/irs-pdf/fw4.pdf
https://www.irs.gov/individuals/tax-withholding-estimator
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
