If possible, I'd suggest you reach out to whomever hired you and ask them the appropriate dress code. If you can't reach anyone, given the position is an accountant, go ahead and pull the interview suit back out.

In general, Its always better to err to being too formal than too informal early on.
Remember the old saying "you never get a second chance to make a first impression".

Don't worry - your colleagues will always let you know if you are overdressed and you can adjust on your second day. (But they don't always let you know when you are underdressed! so be sure to err on the upside).

Congrats to you on your new position.