When I switch will this month’s wages on the 26th be directed straight into my new account
Yes, however
will I have to fill in the new bank details on the back of my wage slip?
In theory, no, but better safe than sorry.
Basically, if you switch via the 7day switching service anything that gets sent to your ‘old’ account will be forwarded to your ‘new’ account. There might be a day’s delay while it’s all processed. So, if it’s something important, best to update the source of the payment too.
Think of it like moving house; you can set up a mail forwarding service, but it’s always best to let the important people know you’re new address…