If your franked mail is coming out faded, streaky or patchy, the fix is almost always one of four things: a dry or empty ink cartridge, a clogged printhead, an unsuitable envelope surface, or an impression printed in the wrong position. Under Mailmark this matters commercially, not just cosmetically, because Royal Mail scans the 2D barcode on every franked item and an impression that cannot be read can be delayed or surcharged. This guide works through the four causes in order of likelihood.
Why print quality matters more under Mailmark
Older franking marks only had to be legible to a human being at a sorting office. Mailmark changed that. Every Mailmark impression carries a 2D barcode holding the account, item and posting data that Royal Mail uses to track and account for your mail automatically, and that barcode has to be machine readable.
Royal Mail's Mailmark barcode definition document shows how tight the tolerances are: a module size between 0.5mm and 0.7mm, print quality meeting ISO 15415 grade 4/A or 3/B, and a clear zone around the barcode of at least four times the module size. In plain English, a smudge or a dry streak across the barcode is enough to break the read.
Royal Mail's Franking Equipment Operational Requirements state that the impression must be clear and legible. If it is not, your item can be delayed or surcharged, quietly erasing the Mailmark discount you franked it for. Since the 2026 Royal Mail postage rates took effect on 7 April 2026, Mailmark franking saves 3p per standard 1st Class letter against a stamp. One surcharged item can wipe out the saving on dozens of others.
Cause 1: the ink cartridge is low, dry or past its best
This is the culprit in most cases. Mailmark machines print in Royal Mail approved blue ink, a formulation designed to give the 2D barcode the contrast Royal Mail's scanners need, and it behaves differently to office printer ink. As a cartridge nears the end of its life the impression usually fades from the bottom or shows white bands where nozzles have stopped firing.
Three practical checks:
- Check the ink level on the machine display, not by eye. Most meters warn well before the cartridge is empty, which is your cue to order a replacement.
- Watch the shelf life. Cartridges have a finite life once installed because the ink can dry in the nozzles. A cartridge in a machine that franks twenty items a week will often dry out before it runs out.
- Use approved ink. Non-approved or badly refilled ink can print the wrong shade, which affects scanning even when the print looks fine to you.
Keeping a spare on the shelf is cheap insurance. Find the right cartridge for your model in our Pitney Bowes ink and label range, our Neopost and Quadient supplies, our FP Mailing Postbase supplies, or the Frama Matrix supplies. If you are unsure which cartridge type your machine takes, our guide to franking machine ink cartridges explains the differences between blue, red and Mailmark ink.
Cause 2: a blocked or dirty printhead
If a new cartridge does not fix it, the printhead is the next suspect. The symptoms are consistent: the same lines missing from every impression, or a mark that starts clean and degrades within a few envelopes.
Almost every franking machine has a printhead cleaning or purge routine in the maintenance menu. Run it once, print a test impression, and run it a second time if needed. Further cycles waste ink, and at that point the head or the cartridge needs replacing rather than cleaning.
Two habits prevent most blockages. Never leave a machine switched off at the wall for long periods with a cartridge fitted, because many machines park and cap the head only when powered down properly. And if the machine sits idle for a week or more, run a test print before your first real batch rather than discovering the problem on 200 customer letters.
Cause 3: the envelope itself
Franking ink needs a surface it can sit on. Heavily textured, laid or glossy envelope stock can cause feathering or beading, where the ink spreads into the fibres or refuses to absorb. Dark or heavily printed envelopes are worse still, because the contrast between the impression and the background drops below what a scanner can resolve.
Damp envelopes are an underrated cause. Stock stored in a cold stockroom or near an exterior wall picks up moisture, and moist paper makes franking ink bleed. Keep envelopes wrapped, indoors, and let a cold pack acclimatise before running it.
If your usual stock is the problem, switching to a smooth, franking-friendly envelope solves it permanently. Our self seal envelopes are chosen for machine feeding and clean ink take-up.
Cause 4: position, thickness and the case for labels
The impression must sit in the top right corner of the envelope with adequate clear space around it. Overlap a window, a fold, a flap edge or a previous mark and the barcode read fails even though the ink is perfect.
Thickness is the other trap. Most desktop franking machines have a maximum item thickness, and forcing a bulky item through skews the feed and smears the mark. For anything too thick, too large or too awkward, a franking label is the correct answer rather than a workaround. Our guide to franking machine labels covers when to use them and how to apply them so they scan.
Check format while you are at it. Items that creep from Letter to Large Letter cost significantly more, and our 2026 postage size guide explains where the thresholds fall. Mailcoms also has a practical overview on avoiding Royal Mail surcharges.
A five-minute weekly routine
Most print quality problems never happen in businesses that spend five minutes a week on the machine. Wipe the feed deck and rollers with a dry lint-free cloth to lift paper dust. Run one test impression and actually look at it, checking the barcode edges rather than just the date. Confirm the ink level and the postage credit, and check that your envelope stock is dry and stored flat.
If the impression is still wrong after fresh ink, a printhead clean and a change of envelope, the machine needs a service engineer rather than another cartridge. Green Franking supplies the consumables, and our sister company Mailcoms supplies, leases and services franking machines across the UK, including Mailmark upgrades where an older meter has been decertified.
The sustainable angle
Every failed impression is a wasted envelope, wasted ink and, if the item is surcharged, a wasted journey through the network. Getting print quality right is one of the least glamorous but most effective ways to cut both cost and waste from your mailroom. Empty cartridges need not go in the bin either: our ink resetting, refilling and recycling service keeps used cartridges in circulation, and you can read more about our approach on our sustainability page.
Frequently asked questions
Why is my franking machine printing faded or streaky?
In most cases the ink cartridge is low, dried out or past its usable life. Fit a fresh approved cartridge first. If the fault persists, run the printhead cleaning routine in the machine's maintenance menu, then check whether your envelope stock is too textured, glossy or damp for franking ink.
Can Royal Mail surcharge mail because of a poor franking impression?
Yes. Royal Mail's franking equipment operational requirements state that the impression must be clear and legible. A smudged, faint or badly positioned Mailmark impression may fail to scan, which can lead to delivery delay or a surcharge on the item.
How often should I clean my franking machine printhead?
Only when print quality drops, plus a test print after any week or more of idle time. Cleaning cycles consume ink, so running them daily costs money without benefit. If two cycles do not restore a clean impression, replace the cartridge or arrange a service visit.
Does the type of envelope affect Mailmark scanning?
It does. Mailmark barcodes are read automatically, so the impression needs good contrast and a clean edge. Very textured, glossy, dark or heavily printed envelopes can cause feathering or low contrast, and damp stock makes ink bleed. Smooth, dry, light-coloured envelopes give the most reliable read.
Should I use franking labels instead of printing directly onto the envelope?
Use labels whenever the item is too thick, too large or too rigid to feed cleanly, and for parcels and packets. Forcing a bulky item through a desktop machine skews the feed and smears the impression, so a label produces a better scan and avoids wasted franks.
Can I use non-approved or refilled ink in my franking machine?
Only Royal Mail approved ink is guaranteed to produce the correct colour and contrast that Royal Mail's equipment expects, so it is the safest choice for reliable scanning. If you want to reduce waste and cost, a professional cartridge resetting and refilling service using approved ink is a better route than generic ink of unknown formulation.