Hi,
VAT numbers are checked based on the setting "VAT number check" in the HikaShop configuration.
Now since the UK is not in the EU anymore, VAT numbers should not be checked anymore I suppose.
You can change the line:
if(empty($zone_code) || !in_array($zone_code,array('AT','BE','BG','CY','CZ','DK','EE','EL','DE','PT','GR','ES','FI','HR','HU','LU','MT','SI',
'FR','GB','IE','IT','LV','LT','NL','PL','SK','RO','SE'))){
to:
if(empty($zone_code) || !in_array($zone_code,array('AT','BE','BG','CY','CZ','DK','EE','EL','DE','PT','GR','ES','FI','HR','HU','LU','MT','SI',
'FR','IE','IT','LV','LT','NL','PL','SK','RO','SE'))){
in the file administrator/components/com_hikashop/helpers/vat.php so that the VAT number is not checked anymore for UK businesses.