Usually, formatting is only needed when there is a problem with the USB flash drive. If this USB flash drive is exclusively sold by the tax authorities, you may be asked to format it after you declare it, but if you buy it yourself in a store, it is unlikely to be formatted for you. The result of formatting is nothing, including other things you put in the USB flash drive yourself. The best way to verify whether the disk is broken or set by the tax department is to try to change the USB flash drive next time.