This will be mainly due to refunds of residential higher rates being made for the next few years (for transactions with an effective date in April 2018 to March 2019).
Y prif reswm am hyn fydd ad-daliadau cyfraddau uwch preswyl am yr ychydig flynyddoedd nesaf (ar gyfer trafodiadau gyda dyddiad dod i rym ym mis Ebrill 2018 i Fawrth 2019).