In order for a granted European patent application to be validated in a State of validation, the application must have been filed in that State on or after the date of entry into force of the Agreement and the State of validation must be designated. For more information on the extension/validation system, please refer to the Examination Guidelines: Extension and Validation of European Patent Applications and Patents for States that are not Parties to the EPC (Examination Guidelines A-III, 12) The validation period varies from country to country, but there is usually a period of three months from the Date of European Grant. within which the national requirements for validation of the country`s phases must be met. In some cases, it is possible to extend this period, sometimes under certain conditions. This usually involves an additional tax. .