Original vs Compatible Franking Ink: A 2026 Buyer's Guide

Ink is the one franking consumable you cannot avoid buying, and it is also the one where the price gap between options is widest. This guide explains what Royal Mail actually requires from franking ink, where original and compatible cartridges genuinely differ, how refilling services fit in, and how to choose without putting your mail at risk of being rejected or surcharged.

What Royal Mail Actually Requires From Franking Ink

Franking ink is not judged on colour or brand. It is judged on whether Royal Mail's automated sorting equipment can read the mark your machine prints.

A Mailmark franking impression carries a 2D barcode, which Royal Mail defines as a Data Matrix ECC200 symbol complying with international standard ISO/IEC 16022. The specification is precise: the module size (each individual square in the barcode) must fall between 0.50mm and 0.70mm, with 0.50mm recommended, and there must be a clear zone around the barcode of at least four times the module size.

On print quality, Royal Mail's barcode definition document states that printing systems should comply with ISO 15415 grades 4/A or 3/B. In plain terms, the barcode has to be sharp, well defined and high contrast. Ink that feathers, fades, smudges or runs dry mid-print can drop the mark below that threshold.

That is the real risk with poor quality ink. If the barcode cannot be read cleanly, your item may be handled manually, which is exactly the outcome a franking machine is meant to prevent. You can read more on our Mailmark technology page.

Are You Allowed to Buy Ink From Someone Other Than the Manufacturer?

Yes. This is settled ground in the UK and has been for two decades.

In 2005 the Office of Fair Trading accepted undertakings in lieu of a market investigation reference from the two leading franking machine suppliers at the time, Pitney Bowes and Neopost, together with Royal Mail. The OFT had found that effective competition had not emerged in aftersales markets including maintenance, inspection and ink cartridge supply. Among the measures agreed was the removal of restrictions on the independent supply of ink cartridges.

That is why an independent franking supplies market exists at all, and why buying your cartridges elsewhere is ordinary commercial practice rather than a grey area.

One caveat: your rental or maintenance agreement is a separate contract. If you lease your machine, read the supply terms in that agreement before switching.

Where Original and Compatible Cartridges Genuinely Differ

Once you strip away the marketing on both sides, the honest differences come down to four things.

Price. Compatible and remanufactured cartridges are consistently cheaper than the manufacturer's own. For a business franking a few hundred items a week, ink is a recurring line in the budget rather than a one-off, so the gap compounds over a year.

Consistency. Original cartridges come from a single controlled production line. Compatible quality varies by supplier, not by category. A well made compatible cartridge from a franking specialist is a different product from an unbranded cartridge bought on a marketplace listing, even if the part number looks identical.

Yield. Cartridges are sold in different volumes, and the number of impressions you get depends on volume, print density and how often the machine sits idle. Compare cost per impression rather than headline price, and check you are comparing the same tank size.

Support. If a cartridge misprints, you want a supplier who understands franking machines and will replace it. That matters far more than whether the box carries a manufacturer's name.

We stock both routes across the major brands, including Pitney Bowes inks and labels, FP Mailing Postbase supplies, Neopost inks and labels and Frama inks and labels.

Refilling Services: The Third Option

There is a route many mailrooms overlook. Some franking cartridges use a chipped tank that can be professionally refilled and reset rather than replaced outright, and this is offered as a service on machines such as the FP Mailing Postbase range and certain Neopost models.

You send the empty cartridge in, it is refilled with approved ink, the chip is reset and it comes back ready to use. It suits businesses with predictable monthly volumes who can plan around a short turnaround, and it reduces the number of plastic tanks going to waste.

It is not right for everyone. If you frank sporadically and cannot afford to be without a cartridge for a few days, keeping a spare on the shelf is the safer approach.

How to Choose Without Risking Your Mail

Work through these in order.

• Match the exact model. Franking cartridges are model specific, not brand specific. A Postbase Qi6 cartridge is not interchangeable with a Postbase Mini one.
• Check the tank size. Many cartridges are sold in 10ml, 20ml and 42ml versions for the same machine. Buying the wrong one is the most common ordering mistake.
• Buy from a franking specialist. A supplier who only sells franking supplies will test against Royal Mail's print requirements and will know the machine you are running.
• Replace before it runs dry. Print quality degrades before a cartridge is empty, and a faint barcode is worse than no barcode.
• Keep your labels in step. Ink quality is wasted on poor stock, so pair it with proper franking labels and suitable franking envelopes.

Frequently Asked Questions

Will using compatible ink invalidate my franking machine warranty?

Buying ink from an independent supplier is lawful and normal following the 2005 Office of Fair Trading undertakings, which removed restrictions on the independent supply of franking ink cartridges. Your warranty or maintenance agreement is a separate contract, so check its supply terms before switching, particularly if you lease rather than own the machine.

Can Royal Mail reject mail franked with compatible ink?

Royal Mail does not assess ink by brand, it assesses the printed mark. What matters is that the Mailmark 2D barcode meets the published specification, including a module size between 0.50mm and 0.70mm and print quality complying with ISO 15415 grades 4/A or 3/B. Good quality compatible ink from a franking specialist meets this, while degraded or unsuitable ink of any origin may not.

How do I know which ink cartridge fits my franking machine?

Check the model name printed on the front of the machine and the part number on your current cartridge, then match both, along with the tank size in millilitres. Cartridges are specific to a machine family and volume, so a cartridge listed for a different model in the same range will usually not fit or will not be recognised by the meter.

Is refilling a franking cartridge better value than buying a new one?

A refilling service is generally cheaper per cartridge than buying new and produces less plastic waste, which suits mailrooms with steady, predictable volumes. The trade off is turnaround time while the cartridge is away, so businesses with irregular or urgent franking usually keep a spare cartridge on hand instead.

The Short Version

The original versus compatible debate is largely settled: the market was deliberately opened up in 2005, and Royal Mail cares about print quality rather than packaging. What matters is buying the correct cartridge for your exact model and tank size, from a supplier who tests against Royal Mail's requirements and will stand behind the product.

Browse our full range of franking ink cartridges and labels to find supplies matched to your machine, or get in touch if you are unsure which version you need.