is my 2012 MacBook pro safe to do my banking on ?

Welcome!

macOS 10.15 "Catalina" is still fully supported and still getting security updates. That status should continue into late 2022 based on a long history of how Apple supports the current OS plus two previous OS versions.

However, a 2012 MBP is maxed out with Catalina so, at some point, it will stop getting updates.

Did something happen with your computer to cause concern or is this a general question? It is fine either way but, were your questioned triggered by some warning or software issue, we may be able to help with that.

If you use secure browsing it is as safe as any other computer.