Is It Legal to Write to Homeowners About Planning Applications? Yes, If Your Letter Does These 6 Things

01

Why “It's on the Public Register” Is Only Half the Answer

Every UK council keeps a planning register by law. In England it is section 69 of the Town and Country Planning Act 1990 and article 40 of the Development Management Procedure Order 2015, which require a register of applications and decisions open to public inspection. Councils may put it online, and almost all do.

The register exists for transparency and consultation: so neighbours can see what is proposed and comment within the consultation period. It was not created as a marketing list. That does not stop you using it, but it shapes the rules.

What the register shows

A typical entry on a council portal shows:

• the site address and the planning reference
• a description of the work, in the council's words
• dates (received, validated, decision) and the status
• often the applicant's name and the agent's (architect's) name and address
• plans, drawings and supporting documents

Anyone can search planning applications near them or check a property's planning history. The scale is big. PlanWatch's own register (377 councils, May to Sep 2026) logged 244,364 applications in five months: 48,873 a month on average. About one in five (18.9%) were classed as householder applications, the extensions, lofts and alterations most trades want.

Why UK GDPR still applies

Personal data is anything that relates to an identifiable living person, directly or indirectly. A householder application is, in practice, “this person's home and their building plans”. Even without a name, an address plus a planning reference links straight back to the applicant on the council portal. So treat the address on your list as personal data, and your letter as direct marketing under UK GDPR.

The ICO's direct marketing guidance makes the point directly: information being publicly available does not mean you are free to use it for direct marketing. You can use it. You just have to use it within the rules below.

02

Letters vs Calls, Texts and Emails: Where PECR Draws the Line

There are two sets of rules, and which one bites depends on the channel.

• UK GDPR and the Data Protection Act 2018 cover the personal data, whatever the channel.
• PECR (the Privacy and Electronic Communications Regulations 2003) adds extra rules for electronic marketing: email, texts, calls. It does not cover post.

That is the whole reason a letter is the safe channel and a phone call is not.

Two traps catch trades out:

1. Looking people up. Taking a name from the register and then finding a phone number, email or social profile is data matching. It adds personal data you were never meant to have and puts you squarely in PECR territory. Don't.
2. Sole-trader agents. If you want to contact the architect or agent on an application at their published business address, remember PECR treats sole traders and some partnerships like individuals for email and text, so they need to have consented first. Marketing emails to limited companies and LLPs do not need prior consent, but they must say who you are and give a valid address for opting out, and you must stop if asked. A letter is still the cleanest route.

03

Your Legal Basis: Legitimate Interests, Not Consent

You do not need the homeowner's consent to send a relevant letter. You do need a lawful basis, and for postal marketing it is almost always legitimate interests (UK GDPR Article 6(1)(f)). The ICO accepts this for post, because PECR's consent rules do not apply.

What changed in 2026

The Data (Use and Access) Act 2025 added wording to Article 6 of UK GDPR saying that processing for direct marketing can be a legitimate interest. It came into force on 5 February 2026. It is a helpful signpost, not a shortcut. Direct marketing is not one of the new “recognised legitimate interests” that skip the balancing test. It is listed only as an example of processing that may be a legitimate interest, and the ICO's updated guidance still expects you to run the three-part test below and record the result. You cannot simply declare something a legitimate interest.

The three-part test

Before you mail, run the ICO's three questions and write the answers down (one page is fine; the ICO publishes a template):

1. Purpose. Is there a legitimate interest? Telling a household that has just applied for building work about relevant local services: yes.
2. Necessity. Do you need this data for it? An address and the planning reference are the minimum to send a letter and explain it. Names, phone numbers and documents are not needed.
3. Balancing. Do the household's interests override yours? This is where you win or lose. The ICO asks whether people would reasonably expect their information to be used this way.

What tips the balance your way

• Relevance. A roofer writing about a dormer is relevant. A conservatory firm writing about a tree application is not.
• One letter, not a campaign. A single, well-timed letter has a low impact. A series of letters pushes the balance the other way.
• No names, no extra data. “The Owner/Occupier”, the address and the reference.
• Transparency. The letter says plainly where the address came from. A letter that cites the planning reference makes the source obvious instead of creepy.
• An easy way out. A clear, free, immediate opt-out, honoured for good.

The case that shows where regulators push

In 2020 the ICO issued an enforcement notice against Experian over offline marketing data on millions of UK adults who had not been told. On appeal, the First-tier Tribunal (2023) and the Upper Tribunal (2024) largely sided with Experian on legitimate interests, accepting it can support offline marketing even where some people might be surprised. What survived was the duty to tell people: the First-tier Tribunal still found Experian should have sent Article 14 privacy notices to people it had not told, and it did not accept the cost of doing so as an excuse, even though it stopped short of ordering fresh notices. For trades the lesson is simple: the legal basis is rarely the problem. Failing to tell people is.

04

The 6 Things Every Planning Letter Must Do

This is the checklist. If your letter does all six, you are on the right side of the line.

1. Go by post, to “The Owner/Occupier”

Post keeps you outside PECR. Addressing the occupier, not a named applicant, keeps the personal data to a minimum. Quote the planning reference so the reader knows exactly why they are hearing from you.

2. Say who you are and where the address came from

Article 14 of UK GDPR applies whenever you get personal data from somewhere other than the person. You must tell them, among other things, who you are and how to contact you, your purpose and legal basis, the legitimate interest you rely on, the source of the data (including that it came from a publicly accessible source), how long you keep it, and their rights.

Timing matters. If you use the data to write to someone, you must tell them at the latest in that first letter. Separately, the ICO's guidance gives one month from obtaining the data as the outside limit, and the safe reading is that both apply. Practical upshot: put the notice on the letter, and mail a list within a month of getting it rather than sitting on it.

3. Explain why you are writing

One or two lines: what you do, why this application made you write, and that your basis is legitimate interests. Keep it human. “We noticed your planning application for a rear dormer and we fit dormers locally” does more work than a paragraph of legal wording.

4. Give a clear, separate way to stop

Article 21(4) says the right to object to direct marketing must be “explicitly brought to the attention” of the person at the latest at the first communication, and presented clearly and separately from other information. In practice: its own box or paragraph, not buried in a footer, with an email, phone number or postal address that actually works.

5. Honour every “stop”, for good

The right to object to direct marketing is absolute. Once someone objects, you must stop using their data for marketing: no argument, no reason needed, no “just one more”. Keep a do-not-mail list (address and date only) and check it before every mailing. That record is the one thing you should keep after you delete the rest of the list.

6. Keep the copy honest

Your letter is advertising, so the CAP Code applies, and consumer protection law (the Digital Markets, Competition and Consumers Act 2024) bans misleading and aggressive practices. That means:

• No council look. No crests, no “Planning Notice” headings, no official-looking envelopes, nothing that implies the council sent it or endorses you. You read a public register; say so.
• Obviously marketing. The reader should know at a glance it is a firm offering a service.
• No false urgency or claims. No “your project must start by…”, no fake “approved contractor” badges, no prices you will not honour.

And keep sensitive details out

Council descriptions occasionally reveal health or family circumstances, for example adaptations for a disabled relative. Never repeat those in a letter, and never open planning documents to personalise one. The Basildon case (see “What to learn from Basildon” below) shows why.

05

Copy This: A “Why You Received This Letter” Notice

Here is an example notice block you can adapt. Print it on the first page, in its own bordered box, in readable type (9pt or larger). It is an example to adapt to your business, not a guaranteed-compliant form: check it against your own set-up.

Why you are getting this letter

[Your business name], [your full postal address], is writing because planning application [reference] for this address is on [council name]'s public planning register. We took the address from that register [optional: using a mailing list compiled by PlanWatch, planwatch.co.uk]. The letter is addressed to the occupier and we have not used anyone's name. We will use the address only to send this letter about [type of work].

We rely on legitimate interests: we think a letter about local [type of work] services is relevant to a household with building plans, and we have weighed that against your privacy.

You can say no. You can object to marketing at any time, free and without giving a reason. Tell us at [email] / [phone] / [postal address] and we will not write to you again.

We keep the address for [period, e.g. 30 days] and then delete it, except on our do-not-mail list if you ask us to stop. You can ask what we hold about you and have it corrected or deleted. You can complain to us, or to the Information Commissioner's Office at ico.org.uk or on 0303 123 1113.

If your list came from PlanWatch

Add two lines to the “You can say no” paragraph:

• “Or go to planwatch.co.uk/stop-mail and enter code [Notice code]. Your address will then come off every firm's PlanWatch-sourced list, not just ours.”
• “Full details of where your address came from: planwatch.co.uk/letter-notice.”

The stop-mail page and the full letter notice are live, and every row in a PlanWatch list carries its own Notice code for this box. Keep the heading “Why you are getting this letter”: the stop-mail page tells households to look for their code in a box with that heading. PlanWatch supplies the code and the two pages, not the notice text itself, so the wording above is yours to adapt.

How to word the rest of the letter

The notice handles the law. The rest of the letter is where you win the job: name the work in the application, show one relevant past job, give one clear next step. Here are real descriptions from the register (council text only, no addresses) and what a good opening line would pick up on:

• Croydon, May 2026: “Erection of rear dormer with Juliet balcony and two rooflights to front and side roof slopes.” A roofer or loft firm leads with dormers and rooflights.
• Bromley, May 2026: “Demolition of existing conservatory and construction of single storey rear extension”. A demolition or groundworks firm leads with clearing the conservatory safely.
• Leeds, May 2026: “Two storey side extension; single storey rear extension; porch to front; rooflights to front and rear”. A builder or scaffolder leads with phasing a two-storey job.
• City of Edinburgh Council, May 2026: “Replace existing timber windows with new white PVC window profiles to match existing.” A window fitter leads with matching profiles.

Refer to the work in your own words. Don't paste the whole description, and never mention anything personal it contains.

06

Mailing Preference Service, the CAP Code and How Often to Write

Mailing Preference Service (MPS)

The MPS lets people register to receive less personally addressed advertising mail. Screening against it is not a legal requirement. It is a condition of the Data & Marketing Association's code for its members, and the CAP Code expects marketers to check lists against relevant suppression files. The ICO's direct marketing guidance says you should check names and addresses against it before mailing.

Because MPS is built around mail addressed to named people, it is generally understood not to cover letters addressed only to “The Occupier”. That is one more reason the occupier format is the cleaner choice. But a household on MPS has told the world it dislikes addressed advertising mail, which is relevant to your balancing test. If someone says they are registered, treat it as an objection and stop.

CAP Code basics for planning letters

• Make it obviously a marketing letter from a business.
• Don't imply council, government or Planning Portal involvement or endorsement.
• Back up any claim you make (“fully insured”, “20 years' experience”, “rated 5 stars”).
• Respect the person's request to stop.

How often to write

One relevant letter per application is the safest pattern, and it is also where most of the response comes from if the timing is right. A single follow-up is a judgement call: note why in your one-page assessment, and send nothing more after any objection. A monthly drip to the same house is where the balance tips against you.

The other frequency problem is across firms. A household that files one application can hear from a roofer, a scaffolder, a builder and a window firm in the same month. That is why a cap on letters per household matters, and why one firm per trade per area is better for everyone, including you. Our trade guides go deeper on timing: how roofers get work, how scaffolders find work and how demolition firms find work.

07

England, Wales, Scotland and Northern Ireland

Data-protection law is UK-wide: UK GDPR, the Data Protection Act 2018 and PECR apply in all four nations, and the ICO regulates everywhere. What differs is the planning system and the register.

PlanWatch's register reads councils in all four nations. Whatever the nation, name the council whose register you used, because that is your “source” under Article 14.

08

How PlanWatch Demand Radar Is Built Around These Rules

Demand Radar is PlanWatch's monthly lead list for trades: a deduplicated, mailing-house-ready list of addresses with relevant planning applications, for one trade in a patch you choose, for £149 a month. It is built with the rules on this page in mind:

• Owner/Occupier, no names. Applicant names are not stored or supplied. Every row is addressed to “The Owner/Occupier”, with the planning reference so your letter can say why you are writing.
• Mail only. Every list comes with the same instruction: “Mail only — no email, no SMS, no cold calls. Each letter should cite the planning reference and carry an opt-out address.”
• A Notice code on every row, for your letter's notice box, so a household can opt out without typing its address.
• A household stop list. A household that uses planwatch.co.uk/stop-mail comes off every firm's future PlanWatch lists, not just yours. It applies to the next batch and to any list downloaded after the request, even one generated earlier.
• A household notice at planwatch.co.uk/letter-notice explaining where the address came from, why, and the household's rights.
• Your own suppression list, applied before every batch, for objectors and anyone you must not mail.
• Exclusive cover: one firm per trade per area if you choose it, checked before you pay, and a cap on letters per household each month across every trade.
• Refused and withdrawn applications dropped, so you are not writing about a project that is not happening.

What it does not do: PlanWatch does not print or post your letters, and it does not write your legal assessment for you. You send the letter, so you are responsible for what it says and for honouring objections. The notice above is the quickest way to get that right. None of this is a statement that any set-up, ours included, is legally compliant or solicitor-approved: our own compliance work is ongoing, and you should check your letters against your own business. PlanWatch's own published case study, on the Demand Radar page, is 500 letters in Hillingdon traced to 35 jobs.

10

How We Counted

• Source: PlanWatch's own planning register, pulled 20 October 2026: applications validated between 1 May and 30 September 2026, from 377 councils.
• Volumes: 244,364 applications in the five months. The monthly figure of 48,873 is that total divided by five (our arithmetic). Council coverage grew to 377 only in May 2026, so earlier months are not comparable and are left out.
• Householder share: 46,220 applications (18.9%) were classed as householder. For most rows the application type is inferred by our scrapers from the description, so treat this as approximate.
• Example descriptions: drawn at random from the window and checked by hand. Rows were filtered out automatically if they contained a name or title, a street or house name, a postcode, a reference number, or any health, disability, child or family wording. Text is the council's description, verbatim.
• Law: summarised from UK GDPR (Articles 6, 14 and 21), PECR, the Data (Use and Access) Act 2025, the planning legislation named above and ICO direct marketing guidance, as at October 2026. Case summaries are from published reports, not the full judgments.

11

Sources

Primary law and regulator guidance this page relies on (checked October 2026):

• UK GDPR Article 6 (lawful basis), Article 14 (information when data is not obtained from the person) and Article 21 (right to object), on legislation.gov.uk
• Data (Use and Access) Act 2025, section 70 (direct marketing as an example of a legitimate interest)
• Privacy and Electronic Communications Regulations 2003, regulation 22 (electronic mail marketing) and regulation 21 (marketing calls)
• Town and Country Planning (Development Management Procedure) (England) Order 2015, article 40 (the planning register)
• ICO: Plan direct marketing, Collect information and generate leads, Legitimate interests, Right to be informed
• ICO statement on the Upper Tribunal ruling in ICO v Experian (April 2024)
• CAP Code, Section 10: Use of data for marketing and the DMA on preference services
• Basildon Borough Council penalty (Local Government Lawyer)