Planning applications must be submitted to your Local Planning Authority (LPA) to receive planning permission for any construction or demolition work you wish to do on your property or land you own. Some works are exempt, but most serious works will require planning permission, so you should always check beforehand.
Once the application is made, the planning department of your local authority will either grant permission (possibly subject to certain conditions) or reject your application. If you have any queries about the application process or regarding the decision you received, you should contact your local authority directly.
Most planning applications can be submitted online and the majority of them are subject to a fee, which varies depending on the type of application you are making and the scope of the project you are preparing the plans for.