it's the force?

Yes, in many places. The imperials have their own credits, both in coin and electronic form.

In the outer rim, where the empire doesn't reach often, planets tend to have their own currencies. Anakin's slavemaster Watto wouldn't accept imperial credits for the hyperdrive repair in episode 1, and wanted 'dactarii' instead. In the Mandolorian, set ~50 years later after the empire fell, the New Republic had it's own currency as well.