@tinker2911 wrote:
We are his next of kin, are we responsible for paying those taxes?
I am sorry for your loss.
You should seek legal counsel (advice) in your jurisdiction but, generally, next of kin are not responsible for paying the federal income tax liability of a decedent unless they have received assets (e.g., real estate, securities, cash) from the decedent's estate. Even then, they could be held responsible only to the extent of the value of the property received.
