What actually works for shared-cost door drops in the UK, and why the American 9x12 card needs rethinking
The shared-cost mailer model is simple: you sell ad spots on one printed piece to a group of local businesses, deliver it to every home in a chosen area, and each advertiser pays a fraction of what a solo distribution would cost.
In the United States that runs on a USPS service called EDDM, built around a large 9x12 inch card. The UK equivalent is Royal Mail Door to Door — around 32 million homes, delivered alongside the regular post, with no personal data involved.
The model works here. The format does not travel unchanged, and that is the single most important thing to understand before you sell anything. This guide covers what the UK actually allows and what to run instead.
Figures below come from the Royal Mail Door to Door User Guide (effective 30 March 2026) and the Whistl Doordrop Media Guide (March 2026). Both change periodically — confirm before your first campaign.
The Thing Nobody Tells You: A 9x12 Card Will Not Go Out Flat
Royal Mail’s item specification is unambiguous:
When folded, items should be smaller than 297mm x 210mm x 5mm and bigger than 148mm x 105mm.
That maximum is A4. The minimum is A6. Whistl, which delivers into the same Royal Mail network, publishes identical limits and notes that items larger than A4 carry an extra folding charge.
Here is how the American co-op formats measure up:
| Format | Size | UK Door to Door |
|---|---|---|
| Standard 9x12 | 228.6x304.8mm | Over A4 on both dimensions — must be folded |
| 6.5x12 | 165.1x304.8mm | Over A4 on length — must be folded |
| Jumbo 12x15 | 304.8x381mm | Well over A4 — must be folded |
| A4 | 210x297mm | Fits flat |
| A3 folded once to A4 | 297x420mm flat | Fits folded |
There is also a 5mm thickness cap and a 100g weight limit on the standard rate card (Whistl offers heavyweights up to 150g).
What to run instead
The natural UK answer is not a smaller card. It is an A3 sheet folded once to A4.
That gives you four A4 panels of space. Measured against a 9x12 card, an A3 sheet carries about 79% more area — so you can sell more ad spots, not fewer, while staying inside the rules. A flat A4 piece works too if you want a lower entry price for smaller markets.
Design in millimetres from the start rather than converting an American template. Inside the 9x12 Agency CRM you control your layout preset and slot sizes, and premium users can resize any Canva ad template to whatever dimensions your UK layout uses.
The Second Thing to Check: the Single Brand Rule
This one deserves a straight answer rather than a comfortable one.
Both Royal Mail and Whistl state that a Door to Door contract can only contain items “clearly identifiable as originating from a single brand, and of a single weight and size” — though you may version items with local details such as store addresses.
A shared card carrying ten unrelated local advertisers is not obviously a single brand. There is a reasonable reading in which your own mailer is the single brand — a locally branded advertising publication that happens to carry advertisers, much like any free local magazine — and that is how most co-op publishers would frame it.
But it is a reading, not a certainty, and it is not worth discovering the answer after ten advertisers have paid you. Call the Royal Mail Door to Door team on 0345 266 0858 (Mon–Fri, 9am–5pm), describe your model plainly, and get their position before you sell. Whistl and other door drop operators are worth a parallel conversation — a private operator may take a different view, and having two routes to market is useful regardless.
This is the single biggest open question for running this business in the UK, and it is much cheaper to resolve in a ten minute phone call than in a cancelled distribution.
Step 1: Plan Your Coverage
Royal Mail offers a free targeting service covering around 32 million UK homes, locally or nationally, without using personal data. Coverage is planned geographically, so you sell an area rather than a list.
As a sense of scale, Royal Mail advertises that around £200 can reach up to 3,000 households — useful for sanity-checking your ad spot pricing before you quote anyone. Get a real quote for your specific area, weight and format before setting prices; rates vary by weight band, and items under 20g attract the most economical rates.
Step 2: Book Your Campaign
You can book through Royal Mail’s online tool, dropaleaflet, or by calling the Door to Door team on 0345 266 0858. Larger or contracted campaigns run through the standard booking system for authorised users, and door drop resellers such as Whistl can book on your behalf.
Two scheduling facts to build into your sales calendar:
- Items must be handed over 7 to 18 days before the start of your distribution. That is a window, not a deadline — too early is as much a problem as too late.
- A single contract can cover distributions over a maximum period of 18 consecutive weeks.
Royal Mail markets a two week turnaround for delivery once your campaign is in. Between selling, artwork, print and the handover window, plan on roughly four to five weeks from “spots sold” to “through the letterbox”.
Step 3: Design Within the Rules
Beyond the size and weight limits, the requirements are light:
- Single piece item. No loose inserts unless the whole thing is in an envelope or securely wrapped, and no loose parts or staples (binding staples inside are fine).
- One design, one weight, one size across the contract.
- Advertising codes apply. Items must comply with the British Code of Advertising and all relevant regulators and laws. Since you are publishing other businesses’ claims, put a line in your advertiser agreement making them responsible for the accuracy of their own copy.
- You may apply a Royal Mail “Delivered by” logo to items actually delivered by Royal Mail. There are no size requirements for it.
Everything else — bleed, CMYK, 300 DPI, print-ready PDF — is universal, and our design and print guide covers it.
Step 4: Print and Hand Over
Print with a UK printer at your finished size. If you are running A3 folded to A4, confirm the printer folds as part of the job — you do not want to fold several thousand sheets by hand, and folding at the distribution end attracts a charge.
Packaging limits at handover:
- Cross-strapped bundles must weigh less than 6.4kg
- Boxes must weigh less than 10kg
- Within a bundle or box, every item should weigh the same and use the same paper weight
Exceed those and your items will not be accepted. Royal Mail offers a Local Handover Service and a Collection and Handover Service; a printer who handles delivery into the network directly can save you the whole exercise.
You will also need to supply a PDF copy of your item before distribution.
UK vs the United States at a Glance
| United States (USPS EDDM) | United Kingdom (Royal Mail) | |
|---|---|---|
| Service name | Every Door Direct Mail | Door to Door |
| Typical format | 9x12 inch card, flat | A4, or A3 folded to A4 |
| Max size | Comfortably takes 9x12 | 297x210x5mm when folded |
| Weight | Priced by weight | 100g standard, 150g heavyweight |
| Hand-off | Drop at the Post Office | Handover 7–18 days before distribution |
| Multi-advertiser | Standard practice | Check the single brand rule first |
Running a UK Agency on the 9x12 CRM
The 9x12 Agency CRM supports agencies outside the United States:
- Campaigns and ad spot pricing in pounds sterling
- Your own white-labelled agency website and booking page
- Layout presets you define — build an A4 or A3 grid rather than a 9x12 one
- Canva ad templates for premium users, resizable to any dimensions
- Online booking and payment, so advertisers pay before you print
→ Try it free at crm.9x12agency.com
Frequently Asked Questions
Can I use a 9x12 card in the UK? Not flat. The limit is 297x210mm (A4) when folded, and a 9x12 card exceeds that on both dimensions. Run A4, or A3 folded to A4 for more ad space.
What is the largest piece I can deliver? Anything, provided it folds down to A4 or smaller and stays within 5mm thick and 100g. Items over A4 attract a folding charge if you do not fold them yourself.
Do I need a mailing list? No. Door to Door targets geographically without using personal data.
Does this work in other countries? Yes, and the format rules are friendlier. See Australia Post Unaddressed Mail and Canada Post Neighbourhood Mail, both of which take a 9x12 card.
How long does a campaign take? Plan four to five weeks end to end. Items are handed over 7–18 days before distribution starts, and Royal Mail markets a two week delivery turnaround.
Is a multi-advertiser card definitely allowed? Confirm it. Contracts must contain items identifiable as originating from a single brand. Your own branded publication is a reasonable reading, but get Royal Mail’s position in writing before you sell spots.
Is Royal Mail the only option? No. Whistl and other door drop operators distribute across UK postcodes, mostly into the same Royal Mail network. Worth a quote either way.
Ready to run campaigns like a real agency? Start free at crm.9x12agency.com, or read the free course starting with why this business model works.
Next read: how to sell ad spots to local businesses · what to charge advertisers
