Mailmark specifications are changing – here’s what you need to know

Mailmark items make up circa 82% of Royal Mail Wholesale volume; they represent excellent value for money and give customers the capacity to monitor the performance of their mailings. The changes below will support customer implementation of the Mailmark specifications, enabling Royal Mail to automate the processing of mail, minimise the need for manual intervention, and ensure that customers continue to benefit from the best price possible.

Whilst we appreciate it is more to read and take on board, the changes make the process and eligibility easier to understand.


To assist minimising the likelihood of Mailmark adjustments being incurred, Royal Mail has categorised each specification point into three risk categories – ‘Mandatory’, ‘RecommendedHigh Risk’ and ‘Recommended – Low Risk’.

New specifications

Royal Mail has developed a redesigned specification for One Piece and Wrap letter items, and new specifications for Perforated letter items, and Do Not Redirect letters.

Royal Mail is making the following changes to the Mailmark Specification:

  • Reducing the minimum height dimension of Letter formats from 110mm to 90mm
  • Clarification of how to apply a reference edge to Letter formats
  • Letter envelopes must be made from paper only and have no open apertures to avoid tearing when processing through automation machines
  • Clarification that the opening flap on an envelope may fold to either the back or the front of mailing item
  • Large Letter windows must be located at least 40mm from the top edge and at least 15mm from the left, right and bottom edges of the envelope
  • Circular windows are permitted for Letters
  • Inclusion of a Letter and Large Letter indicia design print specification
  • Letter and Large Letter indicia design skew requirements relaxed from zero to plus or minus 15 degrees
  • Welsh language addresses may be used when included in PAF
  • The delivery address block skew should be no more than plus or minus 5 degrees
  • Letter and Large Letter print quality clarified such that characters are not blurred, smudged, deformed, or incomplete
  • The delivery address block should not be printed over the edge of the envelope flap
  • Mandatory return addressing requirements added
  • Only one Mailmark 2D code or 4-state barcode must be printed on Letters or Large Letters (the only exception being 4-State Consolidator Barcodes which may be printed onto Letters or Large Letters that bear other Mailmark codes)
  • Clarification of the Large Letter Mailmark codes location requirements
  • 4-state barcode skew added
  • Clarification of border clear zones for poly wrap where the delivery address block is printed on an insert

Any questions?

We’re here to help, so if there is anything you don’t understand or would like clarifying, please get in touch. The above changes can be complied with from now and become mandatory on 16th December 2019