The purpose of this article is to describe the specific function and relevant issues in the expiration of tax obligation related to article 70 of the Act Ordynacja podatkowa. The non-claim of tax obligation means that after a given period, the obligation, though not fulfilled, expires and so does the percentage for the delay. The institution of tax non-claim is a form of guarantee for the taxpayer. In the course of time, the taxpayer’s situation stabilises while it is ensured that his obligation will not change under public law. On the other hand, public administration organs that fail to take appropriate action before the deadline passes cannot interfere in the taxpayer’s rights and duties. The article shows exclusively the rules governing the non-claim procedure of already existing tax obligations and how to properly calculate the time of expiry. It also describes in detail the stopping and suspension of non-claims.