Applying for a patent consists of filing several items with the Patent and Trademark Office. There must be a written document describing the product and what it does. In many cases, a drawing or diagram may be required to illustrate the design or function of the product. The filing fee must also be paid at this time. The Patent and Trademark Office has strict requirements for the manner in which an application must be filed, including the type of paper, margin size, spacing, and page numbering. If all the parts of the application aren't completed correctly, the application must be corrected before the patent registration process can continue. There may be a surcharge for refiling the corrections. Since 19-95, small businesses and individual inventors have been permitted to file a provisional application. This involves a lower initial fee and gives the applicant up to a year to file an official application. During this period, the 'patent pending' mark can be used on the product.