N.H. Rev. Stat. § 87:10
If the amount of the decedent's gross estate, state death tax credit or tax imposed by federal estate tax provisions of the United States Internal Revenue Code of 1986, as amended, shall be increased or decreased by the Internal Revenue Service, such changes shall be reported to the department of revenue administration and the tax imposed by RSA 87:1 upon such estate shall be changed accordingly. Any additional or excess tax shall be reported to the department of revenue administration on an amended return within 90 days after receiving notice from the Internal Revenue Service that a change in the federal estate tax return has been finally determined. Any additional tax shall be paid with such return with interest as prescribed in RSA 21-J:28. Any excess tax received by the state treasurer shall be refunded after the amount shall have been certified to the state treasurer by the department of revenue administration without special appropriation therefor.
RSA 87:10
1931, 125:1. RL 88:10. 1950, 5, part 8, 49:2. RSA 87:10. 1973, 544:10. 1975, 439:26. 1991, 348:11. 1995, 246:4, eff. Aug. 18, 1995.