RSA 75:1-a - http://www.gencourt.state.nh.us/rsa/html/v/75/75-1-a.htm
The appraisal for property tax purposes on multifamily residential rental property which is governed by section 42 of the Internal Revenue Code and which is subject to a recorded housing subsidy covenant that restricts tenant eligibility and rents shall, upon the affirmative request of the taxpayer, be determined under this section. A copy of the recorded land use restriction required by section 42 of the Internal Revenue Code or other low income rental use restriction covenant required by the New Hampshire housing finance authority, is sufficient proof that the property is eligible for assessment under this section.
Application to Municipality - PA-65 – http://revenue.nh.gov/forms/2013/documents/pa-65.pdf
Annual Filing – PA 67 - http://revenue.nh.gov/forms/low-income-housing.htm
To make an election for an appraisal of property subject to a housing covenant under the low-income housing tax credit program, the taxpayer shall, by October 1 preceding the tax year for which the election is sought, provide written notice to the municipality of the taxpayer's election to be assessed under this section, using a form prepared by the department of revenue administration. A property that as of April 1 of the tax year is under construction shall not be eligible to apply for assessment under this section.