If you are not yet using your trademark and decide to file a trademark application, you will have to file the application based on your intent to use the trademark in interstate commerce. When you file your trademark, your effective filing date will be the date on which you filed the trademark application.
However, if the mark that you are trying to register is descriptive, the examining attorney assigned to your trademark application will likely issue an office action refusing registration on the grounds that your mark is merely descriptive. One way to overcome such a refusal is to amend to the Supplemental Register – but this requires that you are using the mark in interstate commerce.
If this is an available option, you should be aware that amending to the Supplemental Register will change your effective filing date to the filing date of the amendment to allege use. This, in turn, may require the examining attorney to conduct a new search for conflicting marks that may have been filed between your old filing date and your new one.
As many do not know that amending to the Supplemental Register can change the effective filing date, it is an important issue to evaluate before making the amendment.