A video decoding method according to the present document comprises a step of deriving transform coefficients for a current block on the basis of residual information, wherein the step of deriving the transform coefficients comprises a step of deriving a zero-out block indicating a region in which effective transform coefficients may exist in the current block, wherein the zero-out block is derived on the basis of flag information indicating whether multiple transform selection (MTS), in which a plurality of transform kernels are used, can be applied to the current block.