A Statement of Use (SOU) is one of the official forms used by the Patent and Trademark Office. It can only be filed once a business has started to use a trademark. This means you can't register a trademark just to tie it up; you need to use it in commerce. Ways to prove a trademark's use include displaying it on products, packaging, or other marketing tools.
If you filed your trademark on the basis of intent to use, you must file a Statement of Use to show you are using it to sell goods and/or services. If you aren't ready to file the SOU, you need to file a Request for Extension of Time to File a Statement of Use within six months of when your Notice of Allowance was issued. The extensions can be filed every six months for up to 36 months.