<prompt> Human: Suppose I have a mortgage on a house. My assumption is that the interest payments are tax-deductible? So heres a question: suppose I get some stocks from my company a windfall, say, worth 50K. If I sell the stocks, it is taxed as income. But what if I sell the stock and put all the money 50K in paying off my mortgage? Assuming interest is 90 of the payments, can I escape all taxes on this 90 of 50K ?  <response>: Assuming interest is 90 of the payments, can I escape all taxes on this 90 of 50K ?Thats not how mortgage payments work. Your interest is calculated as a fixed percentage of the principal balance, not as a percentage of your payment amount. If you pay more than your regular monthly payment, you dont pay any extra interest, the extra money just reduces the principal balance which will actually reduce the amount of interest you pay in the future. Edit: clarity 