N.C. Gen. Stat. § 28A-27-4
The personal representative shall not be under any duty to institute any suit or proceeding to recover from any person interested in the estate the amount of the tax apportioned to the person until the expiration of the six months next following final determination of the tax. A personal representative who institutes the suit or proceeding within a reasonable time after the six months' period shall not be subject to any liability or surcharge because any portion of the tax apportioned to any person interested in the estate was collectable at a time following the death of the decedent but thereafter became uncollectable. If the personal representative cannot collect from any person interested in the estate the amount of the tax apportioned to the person, the amount not recoverable shall be apportioned among the other persons interested in the estate who are subject to apportionment. The apportionment shall be made in the proportion that the value of the interest of each remaining person interested in the estate bears to the total value of the interests of all remaining persons interested in the estate.
N.C. Gen. Stat. § 28A-27-4