People only just learning why there’s strange barcode on Royal Mail post

A man has sparked a discussion on social media after asking whether the ‘black and orange streaks‘ on his letters have a purpose – and it turns out they do.

A man’s curiosity has sparked a discussion after he questioned the purpose of a strange barcode, or ‘black and orange streaks’, on his post.

The intrigued individual took to Reddit, querying: “Does anyone know what these markings are on envelopes?” He also shared images for clarity, adding: “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?”

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Does anyone know what these markings are on envelopes?
byu/One_Tangerine_5201 inWhatisthis

The mystery was soon solved as it was revealed that these marks are known as the Royal Mail 4-State Customer Code (RM4SC), which is crucial for enabling UK postcodes and Delivery Point Suffixes (DPSs) to be read by machines at speed during sorting.

Within Royal Mail circles, this barcode goes by the name CBC (Customer Bar Code). Strict guidelines are in place for the use of these barcodes to ensure their machine readability.

They are frequently utilised by businesses to send large volumes of letters at a reduced cost, and can also be used with Royal Mail’s Cleanmail system.


    Accusoft explains how the barcodes function: “The Royal Mail barcode – also known as the Royal Mail 4-State Customer Code (RM4SCC) – was created by the UK Postal System to automate mail sorting.

    “The term ‘4-State’ refers to the four different bar positions used to encode information, rather than widths. It can encode 5, 6, or 7 character postcodes along with a two-character Delivery Point Suffix (DPS) to ensure mail is correctly 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.”

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