In 2019, taxpayers can choose the provisions according to which they will prepare tax documentation for the year 2018 that has just ended themselves. According to the amended provisions of the CIT Act and the PIT Act, taxpayers can apply provisions that are formally in force as of 1 January 2019 to group transactions concluded already in 2018. Preparing tax documentation according to the new regulations may make things easier for the taxpayer; yet, it may also generate new problems and obligations the taxpayer would not have to face, had they used the earlier regulations.