This includes situations arising as a result of a deliberate inaccuracy in a document given to the WRA by either the taxpayer or someone on their behalf.
Mae hyn yn cynnwys sefyllfaoedd sy’n cael eu hachosi o ganlyniad i anghywirdeb bwriadol mewn dogfen sy’n cael ei rhoi i ACC gan y trethdalwr neu rywun ar ei ran.