How do I know whether my letter is classified as a ‘large’ letter?

A letter is an item which is:

• Up to 240mm in length
• Up to 165mm in width
• Up to 5mm in thickness

A ‘large’ letter is an item which is: 

• Up to 353mm in length
• Up to 250mm in width
• Up to 25mm in thickness

If you have a large letter you must use a ‘large’ stamp. If you are unsure whether your item is a large letter, your post office will be able to help.