Checking ... 12345 6789
could be a UK HMRC VAT code : GB123 4567 89
probably not a UK bank sort code
probably not a UK National Insurance
probably not a UK Postcode
probably not a UK Telephone
probably not an eMail
probably not a IP Address
probably not a IP4 Address
probably not a IP6 Address
probably not a MAC Address
probably not a Regular Expression
probably not a ISO 2 character country code
probably not a ISO 3 character country code