text = '28, king road, new york'
split_text = text.split(', ') # -> ['28', 'king road', 'new york']
if ',' in !TAX_NAME! then !TAX_NAME!.split(',',1)[-1] else ""
if ',' in !TAX_NAME! then !NEW_FIELD!=!TAX_NAME!.split(',',1)[-1] else "".