The estate tax law which applies is that in effect the year his father passed, so 2006. The 2006 estate exemption was $2M. If the amount of his inheritance is less than $2M he is good to go. If it exceeds $2M (based its value in 2006, not value today) then he owes taxes, and is quite likely delinquent and will owe interest and penalties.

Assuming he has a CPA and/or tax attorney handling the estate, he needs to sit down and have a chat. If he doesn't - well, it's time to hire them. His dad needed to file a 2006 tax return even though he was dead - hope this was done.

I've now exceeded the limits of my knowledge on this topic...