What happens to the interest earned at the end of year on mortgage payments?
The interest earned on your mortgage can be used to reduce your supposed tax burden. You can as well consider saving the interest for other purposes. Visit a financial expert or an accountant for more professional advice.
You can deduct the interest you paid when you file your taxes if you itemize. As far as the money you paid to the mortgage company, they earn the interest. Not sure what you are asking exactly.