N.D. Cent. Code § 26.1-24-06: Earned premium

If a peril insured against has existed and the insurer has been liable for any period, however short, the insured is not entitled to a return of premium so far as that particular risk is concerned unless the insurance was for a definite period of time, in which case the insured is entitled to a proportionate return under sections 26.1-24-03 and 26.1-24-05.