N.H. Rev. Stat. § 21-J:43-a

The commissioner of the department of revenue administration and any authorized employee or agent of the commissioner may accept credit cards or debit cards for the online payment of any of the taxes, penalties, interest, or fees administered by the commissioner or collected by the department. The amount of any service charge required to be paid by the taxpayer to the credit card or debit card service provider to cover the provider's cost of this service shall be determined by the department through a competitive bid process, and the service provider shall add this charge to the amount due, in addition to any tax, penalties, and interest payable. The department, at the time of billing, shall disclose the amount of the service charge to the taxpayer. The commissioner shall adopt rules, pursuant to RSA 541-A, as necessary for the administration of such electronic transactions.