People only just realising there’s a ‘hidden’ code on your Royal Mail letters

A man has been left scratching his head after noticing a strange code written all over his post – making him wonder why it’s different on every letter and why it’s there in the first place

It’s one of those things you see almost every day – but never stop to question what it is or why it’s there. But one curious man has sparked a discussion on social media after asking whether the ‘black and orange streaks’ on his letters have a purpose.

Taking to Reddit, he asked: “Does anyone know what these markings are on envelopes?” While sharing a picture to better explain what he means, he added: “I’ve always seen these black and orange streaks on envelopes but never paid them any attention. Today I noticed that there is not a watermark/logo as each one appears to be unique.

“I have attached two pictures: the first is from the Sunday Times and the second is from an estate agent. “My initial thoughts are that they are some sort of digital identifier where the letter gets scanned and then sent to the correct destination, however, why would they be different if they’re both coming to the same place?”

It turns out the markings, known as Royal Mail 4-State Customer Code (RM4SC), have an important purpose – enabling UK postcodes and Delivery Point Suffixes (DPSs) to be easily read by a machine at high speed during the sorting process. For those working within Royal Mail, the barcode is more commonly known as CBC (Customer Bar Code).

There are strict guidelines around the use of these barcodes to ensure they remain readable by machines. They’re commonly used by businesses to enable them to send large quantities of letters at a lower price – but they can also be used with Royal Mail’s Cleanmail system.

Describing how the barcodes work, an Accusoft statement reads: “The Royal Mail barcode — also called the Royal Mail 4-State Customer Code (RM4SCC) — was developed by the UK Postal System to automate mail sorting. The term “4-State” refers to the use of four different bar positions rather than widths to encode information. It can encode 5, 6, or 7 character postcodes along with a two-character Delivery Point Suffix (DPS) to ensure mail is properly sorted and reaches its intended destination.

RM4SCC barcodes can encode numeric digits 0-9, all uppercase letters along with opening and closing parentheses. These codes must be a minimum of 35.98 millimetres wide and a maximum of 68.58 millimetres wide including all encoded data along with start and stop bars. This results in a density of between 20 and 24 bars for each 25.4 millimetres. Worth noting? All bars must be evenly spaced for this code to be properly read by handheld or automatic barcode scanners.”