A multilateral convention implementing treaty-based tax law measures to prevent the erosion of the tax base and the transfer of profits (MLI) modifies double taxation conventions (DTC) in a synchronised manner, without the need for time-consuming bilateral negotiations. In order to check whether a given double taxation convention has been modified by the provisions of the MLI convention, it is necessary to read the synthetic text placed in the table containing the list of double taxation conventions concluded by Poland (https://www.podatki.gov.pl/podatkowa-wspolpraca-miedzynarodowa/wykaz-umow-o-unikaniu-podwojnego-opodatkowania/). For example, in the UPO between Poland and Canada in the context of applying a 5% tax rate to the payment of dividends, the MLI Convention requires the recipient company to hold shares in the capital of the paying company for the entire period of 365 days.