You can use your trademark at any time whether or not it has been officially registered. We recommend filing your application to register your trademark as soon as possible as many Trademark Offices review the legal claims made by companies on a first filed and first used basis.
Take note that if you are conducting business without a registered trademark, you forfeit the advantages and protections afforded by owning a registered trademark. You may be conducting business using the same unregistered trademark as another entity and therefore risk having to protect your right to use the mark in a court of law should the other company try to keep you from using the trademark. Once you file your registration, you do get the benefit of the right to use and the right to conduct business in your Class using the trademark.
We recommend that you file to register your trademark when you plan on using the trademark or are already using the trademark. Some countries request whether the trademark has already been used at the time of filing. Many countries will not allow the trademark to become registered until the trademark is used (usually in these cases extensions of time may be requested) and other countries require a statement of use to be submitted several years after the registration has been granted.