The subject of this article is the issue of choice of law in cross-border transactions and its impact on the contractual interest rates determined by the parties. According to Article 359 § 23 and Article 481 § 23 of the Civil Code, contractual provisions cannot exclude or limit provisions on maximum interest, even if foreign law jurisdiction is chosen. In such event, the provisions of the law shall apply. The quoted rules are therefore overriding mandatory provisions. Thus it is necessary to consider the extent to which these provisions apply, including in particular whether or not the application of polish law in content of interest limits must be done when legal civil relationship between the parties is governed by the foreign law, what derives from an objective coupler.