Anyone mailing ‘periodicals’ (anything officially designated as such qualifies for reduced postage fees) must file their annual Statement of Ownership with the USPS by October 1st.
You can download the form you need here.
Remember that this statement must also be published in the first issue you publish after October 1st.
Per USPS, “failure to file or publish a statement of ownership may lead to suspension of periodicals authorization”.
*If you haven’t signed up for periodicals privileges in the past or need other forms related to periodical mailing, you can find them all here.