N.H. Rev. Stat. § 458:7-a
A divorce from the bonds of matrimony shall be decreed, irrespective of the fault of either party, on the ground of irreconcilable differences which have caused the irremediable breakdown of the marriage. In any pleading or hearing of a petition for divorce under this section, allegations or evidence of specific acts of misconduct shall be improper and inadmissible, except where parental rights and responsibilities are an issue and such evidence is relevant to establish that a particular allocation of parental rights and responsibilities would be detrimental to the child or at a hearing where it is determined by the court to be necessary to establish the existence of irreconcilable differences. If, upon hearing of an action for divorce under this section, both parties are found to have committed an act or acts which justify a finding of irreconcilable differences, a divorce shall be decreed and the acts of one party shall not negate the acts of the other nor bar the divorce decree. The court's findings and decree may be based on oral testimony or written stipulations of the parties.
RSA 458:7-a
1971, 445:1. 1998, 53:1. 2004, 114:2. 2005, 273:2, eff. Oct. 1, 2005.