When you no longer need an existing filter, removing it takes a few simple steps:
1. Click the Gear icon and then Mail Settings.
2. Click the Filters tab (fourth tab to the right).
3. Choose the filter that you would like to delete.
4. Click the delete link located to the right of the filter name.
You have successfully deleted an existing Gmail filter. If you choose to create another filter, you can create the new filter from the Settings menu or by clicking on the Create a Filter link located next to the Search the Web box in any open Gmail Window.
Remember, you can create and edit as many Gmail filters as you like, but only 20 of the filters can be used to forward mail to other email addresses.