U.S. patent law Edit
A notice of allowance and issue fee due is a notification to the applicant that it is entitled to a patent under the law and requesting payment of a specified issue fee (and possibly a publication fee as well) within three months (non-extendable) from the mailing date of the notice of allowance.
U.S. trademark law Edit
A notice of allowance is a written notification from the U.S. Patent and Trademark Office that a specific mark has survived the opposition period following publication in the Official Gazette, and has consequently been allowed for registration. It does not mean that the mark has registered yet. Receiving a notice of allowance is another step on the way to registration.
A "notice of allowance" is issued for a trademark application that has been filed based on intent to use. The notice of allowance is important because the issue date of the Notice of Allowance establishes the due date for filing a statement of use. After receiving the Notice of Allowance, the applicant must file a statement of use or a request for an extension of time to file a statement of use within 6 months from the issue date of the notice. If the applicant fails to timely file a statement of use or a request for an extension of time to file a statement of use, the application will be abandoned.