Royal Mail 4-state Customer Code (RM4SCC)

The Royal Mail 4-State Customer Code (RM4SCC) is a height-modulated barcode symbology used by the UK postal system for automated mail sortation.

The Royal Mail 4-State Customer Code (RM4SCC) is a height-modulated barcode symbology used in the automated mail sortation process.

There are 38 valid characters in the complete character set:

• numeric characters 0-9
• alpha characters A-Z
• open and close brackets ( and ) or [ and ] (used only as start/stop bars)

Complete RM4SCC character set

Each RM4SCC character consists of four bars, of which two are ascenders and two are descenders. The track element is present in all bars.

A complete RM4SCC symbol is made up of a set of distinct bars and spaces for each character, followed by a checksum character and enclosed by a unique start bar, stop bar, and quiet zone. The start and stop bars are unique and different from one another, allowing the symbol to be read in either direction. The quiet zone must be at least 2 mm in each direction.

The checksum character is printed to the right of the data characters to provide error protection. To calculate the checksum character, perform the following steps:

1. Calculate the upper-half and lower-half values for each data character. Each character is split horizontally into an upper half and a lower half. From right to left, assign each bar a weight: the rightmost bar has a weight of 0, the second rightmost 1, the third 2, and the leftmost 4.
2. Based on the presence or absence of an ascender and descender, assign a multiplier to each bar. For the upper half, the multiplier is 1 if the ascender is present, otherwise 0.
3. Multiply the weight and multiplier for each half, then sum the results to produce the combination value for each half. If the combination value equals six, it resets to zero.
4. Sum all the values calculated in step 3 to produce the upper-half and lower-half combination totals. Divide each half's total by six to get the remainder.
5. Look up the table below, using the upper-half combination value as the row reference and the lower-half combination value as the column reference.

Note that the checksum algorithm applies only to the main data characters contained in the code. The start and stop bars do not participate in the checksum calculation.

The customer barcode must be a continuous string of characters and must not include white-space characters. The code density is 20 to 24 bars per 25.4 cm. For detailed requirements on barcode placement and printing, please refer to the UK postal office.