Customs documents must be securely attached to the outside of the box, so customs officers can check what items you're shipping.  You should add 5 copies of the customs documents into a clear plastic envelope or wallet and ensure that this is fastened securely to the outside of the box.
If you do not have a clear plastic wallet or envelope, use a regular envelope clearly marked 'Customs Documents'. For more in-depth information on attaching customs documents, you can learn more here.
Parcel Monkey collects all of the relevant information required for the customs documents during the booking process, so all you need to do is print out the documents and shipping label and attach them both to the box.
If you haven't shipped a package before it's really simple with Parcel Monkey. Check our Customs Advice if shipping overseas to make sure your package clears customs with minimal delays.