That penalty applies if the inaccuracy in the relevant document is due to a failure on the part of the taxpayer (or other person giving the document) to take reasonable care.
Bod cosb yn berthnasol os yw'r anghywirdeb yn y ddogfen berthnasol o ganlyniad i fethiant ar ran y trethdalwr (neu berson arall sy’n rhoi’r ddogfen) i gymryd gofal rhesymol.