My partner died of cancer and a check from her disability insurance came payable to estate. there is no will or administrator.

The first question to ask is whether or not she was entitled to this check from disability.  By this I mean, was she receiving monthly payments and this is another monthly payment?  And you are sure that disability is not going to say "Sorry - the check was sent in error before we knew she passed - pay it back?"  Becuase that happens sometimes.  Social Security and pension checks often arrived after the person has passed, and then are cashed or deposited, but then need to be paid back.  If the check you are talking about is not a monthly check, but is instead sometype of death benefit, then you will need to become the administrator of her estate.  Go to the surrogate's office of the county in which you live. The clerks there will be able to help you.  If you are in Monmouth or Ocean Counties and need further assistance, please feel free to call.