The issue of dating the letter from the Bishop of Olomouc, Robert, to the Archbishop of Gniezno is difficult to determine due to the lack of an annual date in the source. This letter, discovered in the Central Library of the Lithuanian Academy of Sciences, does not contain a full date, but only a daily date. Lithuanian historian E. Gudavičius, dating this source to the beginning of the 13th century, suggests that it could have been addressed to Archbishop Henryk Kietlicz. However, analyzing the context of the letter, it can be concluded that its date can be set at December 21, 1230, which indicates Archbishop Wincenty of Niałek as the addressee. The letter informs about the Pope's decision regarding the collection of tithes from the Hospitaller estates by the papal collector Simon. This is important because it indicates the existence of contacts between Polish and Czech clergy in the 13th century. Robert's letter is a valuable example of contacts between the Polish and Czech clergy in the 13th century, helping to better understand the history of this period.