Investors & landlords

You will need to sign a new contract with the person who has been paying the payments and include his information on the Schedule B along with the interest payment.

Here is some information about your situation concerning the transfer of an installment obligation as a result of the death. You are taxed on the installment payments the same as the seller would have been had they lived to receive the payments, This is from Publication 537 from the IRS. 

With an installment sale, one can report all of the gain in the year of the sale. Or, you may be able to report part of your gain when you receive each payment. You should see which method was used on your mothers taxes; if it was interest only, or if some income was reported each year along with the interest.