Quick answer
Mailmark is Royal Mail's barcode service for machine-readable business mail. Each letter or large letter carries a unique Mailmark barcode, and the mailing is declared to Royal Mail on an electronic manifest (eManifest). Together they let Royal Mail process the mail automatically and give the sender online reporting, including predicted delivery dates. Mailmark matters for cost too: on Royal Mail's April 2026 rate card, an Advertising Mail letter costs 74.0p Standard Unsorted but 42.9p–44.8p Mailmark Unsorted (1,000+ items) and 29.0p–30.4p Economy Low Sort Mailmark (4,000+ items), excluding VAT and levies. Most businesses get Mailmark through an accredited mailing house, which applies the barcodes, sorts the mail and submits the eManifest for them.
Key takeaways
- Mailmark is a unique barcode on every item plus an electronic manifest that describes the mailing to Royal Mail.
- Royal Mail introduced Mailmark in March 2014. By January 2017, 84% of all Access barcoded mail handed over to Royal Mail carried a Mailmark barcode (Royal Mail Wholesale).
- On the April 2026 rate card, Mailmark Advertising Mail letters cost 42.9p–44.8p unsorted and 29.0p–30.4p on Economy Low Sort, against 74.0p for Standard Unsorted (excluding VAT and levies).
- Mailmark reporting shows batch-level performance, predicted delivery and item-level errors, so you can time follow-up activity.
- You do not need your own Royal Mail account or barcode software. An accredited mailing house handles barcoding, sortation and submission.
What is Mailmark?
Royal Mail describes Mailmark as a service that brings mail, technology and business information together. It is designed for high-volume, machine-readable mail, which means letters and large letters that Royal Mail's sorting machines can read without manual handling.
A Mailmark mailing has two parts:
- A Mailmark barcode on every item. It identifies the item uniquely and tells Royal Mail's machines how to handle it.
- An electronic manifest (eManifest). It describes the whole mailing, including volumes, service and sortation, and is submitted to Royal Mail before handover.
Royal Mail introduced Mailmark in March 2014. It replaced the older CBC barcode service for bulk mail, which Royal Mail planned to withdraw from 1 January 2018 once most machine-readable mail had switched to Mailmark.
Mailmark for bulk mail and for franking
You may also see 'Mailmark' on franking machines. Royal Mail's barcode specification covers several types of Mailmark item, including bulk sorted and unsorted mail, franking and online postage. This guide is about bulk business and marketing mail, which is what a mailing house produces.
How the Mailmark barcode works
Royal Mail's Mailmark Barcode Definition Document sets out two kinds of barcode. Most mailings use the 2D version.
| 2D Mailmark barcode | 4-state Mailmark barcode | |
|---|---|---|
| What it looks like | A square or rectangular Data Matrix code (ISO/IEC 16022) | A line of bars of four different heights |
| Sizes | Type 7 (24 × 24 modules), Type 9 (32 × 32) or Type 29 (16 × 48) | One format |
| Space for the sender's own data | Yes: 6, 45 or 25 characters depending on the type | No |
| Who uses it | Most mailers and mailing houses | Mailers who cannot print 2D barcodes |
The barcode holds the class of mail, a Supply Chain ID that identifies the group of companies involved in the mailing, and an Item ID that identifies the individual item. Royal Mail requires each item to stay uniquely identifiable for at least 90 days.
The spare space in a 2D barcode can hold the sender's own reference. Royal Mail suggests uses such as managing print runs, handling returns and goneaways, and identifying items in a particular campaign. This customer data does not flow through to Mailmark reporting, but it can be read back when items are returned.
Leave room for the barcode
A 2D Mailmark barcode is between 12 mm and 22.4 mm square, or 8–11.2 mm by 24–33.6 mm for the rectangular type. Plan space for it near the address when you design letters, self-mailers and envelope windows. A good mailing house will check this at artwork stage.
How Mailmark lowers postage costs
Royal Mail prices Mailmark services well below unbarcoded mail. The prices below are per letter (up to 100g) for Advertising Mail, Royal Mail's service for marketing mailings, from the retail price guide effective 7 April 2026.
| Advertising Mail letter, up to 100g | Price per item | Minimum volume |
|---|---|---|
| 2nd class stamp (for comparison) | 91p | None |
| 2nd Class Standard Unsorted (no Mailmark) | 74.0p | None |
| 2nd Class Mailmark Unsorted | 44.8p (1,000–2,499) to 42.9p (10,000+) | 1,000 items |
| 2nd Class Low Sort Mailmark | 39.0p to 37.2p (80,000+) | 4,000 items |
| Economy Low Sort Mailmark | 30.4p to 29.0p (80,000+) | 4,000 items |
74.0p
Advertising Mail 2nd Class Standard Unsorted letter, no Mailmark
Source: Royal Mail, April 2026
30.4p
Advertising Mail Economy Low Sort Mailmark letter (4,000–79,999 items)
Source: Royal Mail, April 2026
Two things drive the saving: the Mailmark barcode itself, and how far the mail is sorted before handover. Low Sort prices need at least 4,000 items. In our experience, Mailmark sortation often cuts postage by 15–30% compared with unsorted mail. See how much direct mail costs for the full breakdown, including print and enclosing.
Mailmark sortation, done for you
We print, personalise, enclose and sort your mailing to Mailmark standard at our Keighley site, then manage submission to Royal Mail.
Explore the serviceMailmark reporting and tracking
Because every item is barcoded and the mailing is declared on an eManifest, Royal Mail can report on how the mail moves through its network. Royal Mail Wholesale lists these features:
- Batch-level reporting, including volumes, performance and predicted delivery dates.
- Item-level error reporting, which flags problems with individual items such as unreadable barcodes or poor address data.
- PDF reports on request, and Direct Data, which supplies item-level data automatically.
Predicted delivery is the most useful feature for marketers. If you know when a mailing is due to land, you can time follow-up emails, calls and staffing around it. For a charity appeal, for example, you can make sure the donation line is staffed on the right days. Plan the whole campaign around those dates.
Reporting is an indication, not proof of delivery
Royal Mail's terms describe Mailmark reports as an indication of a batch's performance. Some items will never be read by the processing machines, and item-level data cannot be used to claim refunds. Treat Mailmark as tracking at mailing level, not as a signed-for service.
How to send mail using Mailmark
Sending Mailmark mail yourself means applying compliant barcodes, sorting to Royal Mail's rules, building and submitting the eManifest, and registering with Royal Mail. Most organisations hand this to a mailing house instead.
- 1
Check your volume and format
Mailmark Unsorted Advertising Mail starts at 1,000 items and Low Sort at 4,000. The item must be a machine-readable letter or large letter.
- 2
Design with the barcode in mind
Leave space for the barcode near the address, and keep text and graphics clear of it. Your mailing house will tell you where it can go.
- 3
Prepare your data
Clean, PAF-validated addresses improve sortation and reduce the errors that show up in Mailmark reports. Our data processing team handles this.
- 4
Print, enclose and barcode
The barcodes are printed on each item or its envelope during production, usually alongside the personalisation.
- 5
Sort, manifest and hand over
The mailing house sorts the items, submits the eManifest and hands the mail to Royal Mail or a downstream access carrier.
Fretwell is a Royal Mail Approved Mailing House and Mailmark accredited supplier, so there is no need for you to hold your own Royal Mail account. See our certifications for details. Use the direct mail campaign checklist to make sure nothing is missed before handover.
Mailing to Ireland?
Mailmark is a Royal Mail service for UK mail. For mailings to the Republic of Ireland, An Post has its own system for bulk mail. See PostAim explained and our Ireland direct mail service.
Sources
- Royal Mail Wholesale – Royal Mail Mailmark
- Royal Mail – Mailmark Barcode Definition Document, issued 25 September 2020
- Royal Mail Wholesale – Withdrawing Access CBC service, customer letter, 16 March 2017
- Royal Mail – Mailmark Participant Terms & Conditions
- Royal Mail – Retail Letters Price Guide, prices effective 7 April 2026 (archived copy)
- Royal Mail – UK stamp prices from 7 April 2026 (archived copy)
