The information you need to link your Halifax current account to Plum is:
This is the first field in Online Banking. It is 9-30 characters long and contains letters and numbers.
The second field on the first page of Online banking.
3. Memorable information
Your memorable information has 6-15 characters and contains at least 3 letters and 1 number. It does not have spaces, hyphens or special characters.
If you have problems accessing your bank account you can find Halifax instructions here.