Unjustified enrichment may occur where the taxpayer has not ultimately borne the cost of the tax that would otherwise be repaid or discharged and has already collected it from someone else.
Gall cyfoethogi anghyfiawn ddigwydd lle nad yw’r trethdalwr wedi ysgwyddo cost y dreth y byddai angen ei had-dalu neu ei rhyddhau fel arall ac sydd eisoes wedi'i chasglu gan rywun arall.