Royal Mail Urges Everyone to Write 'Two Words' on Post
The next time you seal an envelope, it is worth checking more than the stamp and the address on the front. Royal Mail recommends including a return address, giving the postal service somewhere to send an item if it cannot be delivered.

TL;DR
- Royal Mail recommends including a return address on all mail.
- The words 'Return Address' should be written above the sender's details.
- The return address is useful for undelivered mail, especially important items like gifts or paperwork.
- For standard letters, the return address can be placed on the back, with name and full address including postcode.
- Clear recipient addresses and postcodes are also crucial for efficient mail processing.
- Adding a return address improves the chances of undelivered mail being returned to the sender.