Direct debits

[MongerTruffle]

Is it ten working days' or fourteen calendar days' notice that needs to be given to amend a direct debit? I changed the amount of my British Gas payment just before Christmas and I can't work out when my payment this month is (it would normally be on the 1st).

It can vary and depends on their set up and the day and time you requested the adjustment. They should send you a confirmation sheet saying when.
I would suggestion that it will call for regular amount 2nd Jan then the adjusted amount thereafter.