Sections 8 and 15 Affidavits are considered post-registration filings.
Affidavit of Use (“Section 8” Affidavit)*
An Affidavit of Use under 15 U.S.C. § 1058 (“Section 8”) must be filed between the fifth and sixth years of registration. This filing proves that the mark is still being used in commerce. A six-month grace period for filing the Section 8 exists as long as the required fee is paid. Please note that a Section 8 affidavit is required in order to maintain your registration. Failure to file the required Section 8 affidavit will result in the automatic cancellation of your registration by the U.S. Patent & Trademark Office.
For registrations issued under the Madrid Protocol, the Section 8 affidavit is known as a Section 71 affidavit.
Affidavit of Incontestability (“Section 15” Affidavit)
If the mark is registered on the Principal Register, the registrant may also file a Section 15 Affidavit of Incontestability, 15 U.S.C. § 1065. The registrant must declare in the affidavit that the mark has been in continuous use in commerce, on or in connection with the goods or services covered by the registration, for a period of five years after the date of registration. Although a Section 15 affidavit is an optional filing, incontestability status provides the registrant with a powerful advantage should it need to bring suit for infringement, namely, conclusive evidence of the validity of the registered mark and its registration, of the registrant’s ownership of the mark, and of the owner’s exclusive right to use the registered mark in commerce. As mentioned above, the Section 15 filing is optional. Failure to file a Section 15 affidavit will not result in the cancellation of your registration.
 Currently, the fee for filing a Section 8 Affidavit is $125 per class, and the fee for filing within the six-month grace period is also $100 per class.
 The fee for filing a Section 15 affidavit is currently $200 per class. Since the time for filing a Section 15 often coincides with the time for filing a Section 8, most registrants file a Combined Affidavit of Use and Incontestability.
 Section 14 of the Trademark Act, 15 U.S.C. § 1064, limits the grounds that a third party can raise in a petition to cancel a mark registered on the Principal Register when the petition is filed more than five years from the date of registration or publication under § 12(c). This limitation of grounds does not depend on the filing of a §15 affidavit.
* For registrations based on WIPO Interntational Registrations, the Section 8 affidavit is known as a Section 71 affidavit, but the requirements are the same.