If it is password protected and FileVault is enabled, but not iCloud locked (so it’s asking for an admin account password, not an Apple ID password) . Boot into recovery mode (press and hold cmd+ r at boot). When it’s on the screen asking for an administrator account password , click the Apple menu in the top left corner and there should be an option to Erase this Mac. One that’s done you can reinstall the OS and start all over.
If it is iCloud locked, or was enrolled in any sort of device management through the business, it may still ask for a password or credentials in order to activate the device once it was erased. If that is the case, the company would need to unlock it for you in order for it to be usable.