From the 16th December there will be changes to the Mailmark Letter and Large Letter specifications.

Below is a summary of the changes, but if you would like to discuss any of these, please to get in touch with your ONEPOST Account or Business Manager.  We’re here to help.

Summary of Changes:

  • 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 our 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 polywrap where the delivery address block is printed on an insert.

For full details of these specifications see Royal Mail User Guide Change to Mailmark Specification