A method for implementing an adaptive colour transform (ACT) mode during image/video encoding and decoding includes performing a conversion between a current video block of a video and a bitstream of the video, wherein the current video block is coded using the ACT mode, wherein the conversion comprises applying an inverse ACT transform on the current video block according to a rule, and wherein the rule specifies that a clipping operation, based on a bit depth of the current video block, is applied to an input of the inverse ACT transform.