En español | Federal law requires that Social Security checks be cashed or deposited within one year of the date of issue. Uncashed checks are void after that time.
The Treasury Department has a process for filing a claim for replacement of amounts due a deceased beneficiary. This process must be completed within 6 years of the check being issued. If you can cash the checks you will not be able to keep the money.
By law, the money would belong to the deceased's estate. If the estate has already gone through probate, there are legal procedures for reopening the probate to distribute the money to the proper heirs.