Where a landfill site operator has authorised an agent to act on their behalf, the tax return must contain a certification by the agent that the operator has declared that the return is correct.
Pan fo gweithredwr safle tirlenwi wedi awdurdodi asiant i weithredu ar ei ran, rhaid i'r ffurflen dreth gynnwys ardystiad gan yr asiant bod y gweithredwr wedi datgan bod y ffurflen yn gywir.