Royal Mail Mailmark 4-State
Barcode C (22 characters) for consolidators, barcode L (26) for everyone.
Create Royal Mail Mailmark 4-State ›Used by 700,000+ people
Free Royal Mail Mailmark barcode generator.
Mailmark identifies each item of a Royal Mail bulk mailing, in 4-state bars or a Data Matrix. Type the data string and download the barcode.
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How to create a Royal Mail Mailmark barcode
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01
Join the fields
Write format, version, class, supply chain ID, item ID, then postcode and delivery point suffix (DPS), padded to 9 characters: 26 in all for barcode L, 22 for C.
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02
Set 300 dpi and the module width
Set Resolution 300. For the 4-state type, keep Module width at Fit and switch off the human-readable text; a millimetre width removes the bars. For Mailmark 2D, choose Module width Pixel 6 for 0.51 mm modules (Royal Mail: 0.50–0.70 mm).
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03
Download PNG and add a clear zone
The image has no clear zone. Leave 2 mm around a 4-state barcode and 4 modules around Mailmark 2D, on the side with the indicium and address.
What is a Royal Mail Mailmark barcode?
A Royal Mail Mailmark barcode is the code a mail piece needs for Royal Mail's Mailmark options in Retail and Network Access. Mailmark 2D is a Data Matrix with room for your own data; the 4-state barcode C or L serves customers who cannot print 2D codes.
Where Mailmark is printed: bulk letters, large letters, parcels
Mailers and mailing houses print a Mailmark on every item of a sorted or unsorted bulk mailing. Its item ID must stay unique for at least 90 days. Consolidators may use barcode C with a 2-digit supply chain ID; barcode L, with 6 digits, is open to all customers.
Both 4-state types may go on Manual Mailmark parcels and general large letters. A 2D Mailmark carries your own reference too, for returns or a campaign.
Printing a Mailmark the sorting machines can read
Royal Mail reads both kinds with one image capture system and measures each item's progress through its automation. 4-state bars must be darker than the background, at a symbol contrast ratio of at least 40%; Mailmark 2D should reach ISO 15415 grade 4/A or 3/B.
The generator's 4-state bars are about 0.5 mm wide at 24 per inch, within Royal Mail's limits. With the human-readable text on, full bars are only 2.54 mm high, below the 4.22 mm minimum; with it off at 300 dpi, they are 5.33 mm.
From a test print to a full mailing
The online generator makes Mailmark barcodes for free as GIF, PNG or JPG; SVG and higher print resolution come with a plan. Without an account it makes one at a time; a mailing, with unique item IDs, belongs in a data sheet, which makes many barcodes after a free sign-in.
TEC-IT software has Mailmark 2D and 4-state as symbologies of their own; TBarCode SDK applies the required C40 encoding. TFORMer Server prints a mailing from ERP data unattended, and the TBarCode API answers an HTTP request with the barcode image.
Royal Mail Mailmark at a glance
- Type
- 4-state C and L; 2D Data Matrix ECC200
- Specification
- Mailmark Barcode Definition Document 1.6 (2025)
- Length
- C 22, L 26 characters; 2D 45 plus customer content
- Symbol size
- C 66 bars, L 78 (about 89 mm at 21.2 per inch); 2D 24 × 24, 32 × 32 or 16 × 48 modules
- Error correction
- 4-state at least 25%; 2D ECC200
- Bars and modules
- Bars 0.38–0.63 mm, 20–24 per inch; 2D modules 0.50–0.70 mm
Mailmark data fields and their lengths
Fields have fixed lengths, and spaces fill missing values.
| Field | C | L | 2D |
|---|---|---|---|
| Identifier | — | — | JGB, a space, information type |
| Format or service type | 1 letter, 2 large letter, 4 parcel | Same as C | After the postcode: 0 letter, 1 large letter, 4 parcel |
| Version, class | 1 + 1 | 1 + 1 | 1 + 1 |
| Supply chain ID | 2 | 6 | 7 |
| Item ID | 8 | 8 | 8 |
| Postcode and DPS | 9 | 9 | 9 |
| Return postcode, reserved | — | — | 7 + 6 |
| Customer content | — | — | Type 7: 6, Type 29: 25, Type 9: 45 |
Royal Mail's 4-state print sizes
| Measure | Recommended | Acceptable |
|---|---|---|
| Ascender, descender (beyond tracker) | 1.90 mm | 1.60–2.16 mm |
| Tracker | 1.30 mm | 1.02–1.52 mm |
| Full bar | 5.10 mm | 4.22–5.84 mm |
| Bar width | 0.54 mm | 0.38–0.63 mm |
| Pitch | 21.2 bars per inch | 20–24, equally spaced |
Mailmark compared with related barcodes
Royal Mail 4-State ›
Four bar heights, up to 9 postcode characters plus a check character; used for CBC mailings, no longer offered for Retail and Network Access.
Data Matrix ›
Mailmark 2D's symbology, without the JGB prefix and fixed fields.
KIX ›
Dutch postcodes in 4-state bars; the same 2 mm quiet zone, no check digit.
Which Mailmark type to pick
Royal Mail Mailmark 2D
The 45-character Royal Mail part, then your own content; the generator picks the symbol size from the data.
Create Royal Mail Mailmark 2D ›Frequently asked questions
Learn more about Royal Mail Mailmark.
What is the difference between Mailmark barcode C and L?
Barcode C, for consolidators only, holds 22 characters in 66 bars with a 2-digit supply chain ID. Barcode L, open to all, holds 26 in 78 bars with 6 digits. On an item with both, Royal Mail gives the consolidator code preference.
Which Mailmark barcode should I use for large letters?
Royal Mail's 2014 selection chart calls 2D Types 9 and 29 the most suitable for large letters. Whichever type you print, mark the item as a large letter in the data: format 2 in a 4-state code, service type 1 in Mailmark 2D.
Can I put my own data in a Mailmark barcode?
Only in Mailmark 2D: 6 characters in Type 7, 25 in Type 29 and 45 in Type 9, none of which reaches Mailmark Analytics. Lower case and punctuation take more room. Leave unused space empty, not filled with spaces, to keep more error correction.
How can I check that my Mailmark barcode is correct?
Royal Mail checks barcode samples sent as a PDF or a physical mail piece. For Mailmark 2D, a scanner or verifier that shows how the data was encoded tells you whether the Royal Mail fields use C40, as Royal Mail requires.
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The developer package for Windows: .NET, OCX and DLL components generate and print 100+ barcode symbologies from your applications.
ProductTFORMer Server
Your ERP sends the data – labels and forms print around the clock, unattended.
ProductTBarCode API
Request a barcode by URL and get an image back – no installation, no platform lock-in, the same engine behind every TEC-IT product.