It is a scam.  Don’t click on the link, just delete the email.

Dear Halifax Customer
During our regularly scheduled account maintenance and verification procedures, we have detected a slight error in your billing information.

This might be due to either of the following reasons:
A recent updates in our billing server ( Due to slightly problem )
A recent change in your personal information ( i.e. change of Question ).
An inability to accurately verify your selected option of payment due to an internal error within our   processors.

Please update and verify your information by clicking the link below:  

https://www.halifax-online.co.uk/update/straightup.no/language/Login.asp?source=halifaxcouk

If your account information is not updated within 48 hours then your ability to access your account will become restricted.
Thank you