Various implementations for video encoding and decoding are presented involving determining, for a block being encoded or decoded in a picture, a coefficient group mode for coding at least one coefficient of a set of transform coefficients of the image block; encoding or decoding the set of transform coefficients of the image block responsive to the coefficient group mode. The coefficient group mode can be determined from at least one of image block size, number of non-zero transform coefficients inside the image block, position of a transform coefficient inside the image block, decoded syntax element, wherein the coefficient group mode can specify whether a coefficient group significance flag is coded/decoded, indicating that at least one coefficient is non-zero inside a coefficient group and/or specify at least one size of the coefficient group.