I am tracking my credit rating with Experian, CretiKarma and Clearscore. In the last 2 months it has gone down and the only change to it is that that I have opened two more bank accounts. My current banking(Halifax) that I have been using for 5 years and a new Natwest account (less than a 4 months old) and a new Monzo account(for traveling purposes also less than 4 months old). Does multiple bank accounts reduces your Credit rating.
Does multiple bank accounts reduces your Credit rating
The answer depends on the type of account. If it is a loan, it will show up on your credit report and will impact your score. A deposit account won't show up and won't impact your score.
There may be other, less obvious things happening with respect to your credit report, which may also be impacting your score. For instance, if an old, long-since-closed account has recently reached the age threshold at which it is no longer included in your score, you may see a change even though you didn't actually do anything different today to trigger it. There are many online resources that explain the factors that go in to credit scores in the general sense, but if you're already registered with a service like CreditKarma, you should be able to utilize that service to see the specific changes to your report on a monthly basis, which should tell you exactly what caused the change.
Presumably when you opened the bank accounts there would be hard inquiries run when the banks checked your history. Hard inquiries only have a small temporary negative effect on your score, and your score should go back up within about 6 months. If that doesn't explain the dip then perhaps something else changed about your credit profile; for example, credit line utilization percentage tends to slightly fluctuate month to month for most people.
In short, some credit referencing agencies think older accounts indicate stability (I think Experian mentions it), so may give you a lower score for a while if you open new current accounts.
But it is just a scoring they have decided. Lenders may ignore it entirely and you could argue that a "savings score" would be just as relevant.