N.H. Rev. Stat. Ann. § 540-A: § 540-A:6

I. (a) A landlord shall not demand or receive any security deposit in an amount or value in excess of one month's rent or $100, whichever is greater. Nothing in this section shall prohibit a landlord from entering into a written lease that requires the quarterly or less frequent payment of rent; provided, however, that the security deposit received in addition to the initial rent payment may not exceed the equivalent of one month's rent.
(b) Except as provided in subparagraph (c), upon receiving a deposit from a tenant, a landlord shall forthwith deliver to the tenant a signed receipt stating the amount of the deposit and specifying the place where the deposit or bond for the deposit pursuant to RSA 540-A:6, II(c) will be held, and shall notify the tenant that any conditions in the rental unit in need of repair or correction should be noted on the receipt or given to the landlord in writing within 5 days of occupancy.
(c) No receipt shall be required when the tenant furnishes a security deposit in the form of a personal check, a bank check, or a check issued by a government or nonprofit agency on behalf of the tenant. Regardless of whether or not a receipt is required, the landlord shall provide written notice to the tenant that a written list of conditions in the rental unit in need of repair or correction, if any, should be given to the landlord within 5 days of occupancy.
II. (a) Security deposits held by a landlord continue to be the money of the tenant and shall be held in trust by the person with whom such deposit is made and shall not be mingled with the personal moneys or become an asset of the landlord until the provisions of RSA 540-A:7 are complied with, but may be disposed of as provided in RSA 540-A:6, III.
(b) A landlord may mingle all security deposits held by him in a single account held in trust for the tenant at any bank, savings and loan association or credit union organized under the laws of this state in satisfaction of the requirements of RSA 540-A:6, II(a).
(c) A bond written by a company located in New Hampshire and posted with the clerk of the city or town in which the residential premises are located in an amount equivalent to the total value of a security deposit held by the landlord on property in that city or town shall exempt the landlord from the provisions of RSA 540-A:6, II(a) and (b).
III. (a) Any landlord who holds a security deposit shall turn the security deposit over at the time of delivery of the deed or instrument of assignment, or within 5 days thereafter, or within 5 days after a receiver has been qualified, to one of the following:
(1) his grantee upon conveying the premises in which the rental unit is located;
(2) his assignee upon assigning his lease to the rental unit;
(3) the receiver in a foreclosure action or other lien of record affecting the property in which the rental unit is located, upon the judicial appointment and qualification of the receiver; or
(4) the purchaser at a foreclosure sale or other lien of record, if a receiver has not been qualified, upon the conveyance to another person by the referee of the property in which the rental unit is located.
(b) The landlord shall notify the tenant by registered or certified mail of such turning over, including the name and address of the grantee, assignee, purchaser, or receiver who then holds the security deposit.
(c) Any landlord who turns over to his grantee, his assignee, a purchaser at a foreclosure sale, or the receiver in a foreclosure action the amount of such security deposit with interest due, if any, is thereby relieved of liability to the tenant for repayment of the deposit. The transferee of the security deposit is then responsible for the return of the security deposit to the tenant or licensee, unless, before the expiration of the term of the tenant's lease or licensee's agreement, he transfers the security deposit to another, pursuant to RSA 540-A:6, III(a) and gives the requisite notice pursuant to RSA 540-A:6, III(b). A receiver shall hold the security subject to its disposition as provided in an order of the court to be made and entered in the foreclosure action.
(d) RSA 540-A:6, III(c) shall not apply if there is an inconsistent agreement between the landlord and tenant or licensee.
IV. (a) A landlord who holds a security deposit for a period of one year or longer shall pay to the tenant interest on the deposit at a rate equal to the interest rate paid on regular savings accounts in the New Hampshire bank, savings and loan association, or credit union in which it is deposited, commencing from the date the landlord receives the deposit or from September 13, 1977, whichever is later. If a landlord mingles security deposits in a single account under RSA 540-A:6, II(b), the landlord shall pay the actual interest earned on such account proportionately to each tenant.
(b) Upon request, a landlord shall provide to the tenant the name of any bank, savings and loan association, or credit union where his security deposit is on deposit, the account number, the amount on deposit, and the interest rate on the deposit and shall allow the tenant to examine his security deposit records.
(c) Notwithstanding RSA 540-A:7, I, a tenant may request the interest accrued on a security deposit every 3 years, 30 days before the expiration of that year's tenancy. The landlord shall comply with the request within 15 days of the expiration of that year's tenancy.