In short and in plain language
Some firms work together. For example an electrician, a plumber and a painter. They want one website for all of them.
Each firm gets its own part there. It says clearly who does the work.
In the form, the customer ticks what he needs. Only these firms then see his request.
The legal notice lists each firm with its name and address. The firms agree in writing who takes care of data protection.
We help you build the site.
An electrical firm, a plumbing and heating firm and a painting firm have worked on the same sites for years. At some point the idea comes up to offer the work together: bathroom or old-building renovation from a single source, one contact, one website. For customers that is convenient. For the three firms, less changes legally than the joint appearance suggests: they remain three businesses with three entries in the register of skilled trades, three addresses and, as a rule, three separate areas of responsibility under data protection law. The website has to show both, the joint offer and the separate firms behind it. 94 percent (Bitkom 2025) of the trade businesses surveyed already use a website of their own, so the cooperation site usually comes on top and replaces nothing. This article shows how such a site is structured, how requests reach the right firm, what the legal notice must state for each partner and who is responsible for what under data protection law.
Key takeaways
- First settle who the contracting party is: each firm on its own, one lead firm or a joint company. If partners run a business under a common name, their GbR is presumed to enter into contracts itself (§ 705(3) BGB).
- One page per trade naming the firm that does the work, plus a shared home page and a page on the process. Do not copy texts from your own website: 94 percent of the firms surveyed already use one (Bitkom 2025).
- The request form asks for the trade and sends the request only to the firms selected. A shared inbox in which everyone reads everything sits poorly with data minimization (Art. 5(1)(c) GDPR).
- The legal notice lists every participating firm with all details under § 5(1) DDG. The blocks differ: 67.5 percent of the trade businesses covered are sole traders, 24.2 percent are GmbHs (ZDH, Handwerkszählung 2024).
- If the firms decide on the website and the form together, they are usually joint controllers for them (Art. 26 GDPR). They conclude an arrangement and make its essence available on the website.
- The arrangement sets out who answers access requests within one month (Art. 12(3) GDPR) and who reports a data breach, where feasible within 72 hours (Art. 33 GDPR). Data subjects can still turn to any of the firms.
First settle who the contracting party is
Before a single page is designed, there is a question that has nothing to do with design: with whom does the customer sign the contract? It determines who appears in the legal notice, who takes the request, who writes the quote and who is liable if something goes wrong. In practice there are three models, and each calls for a slightly different website.
| Model | Customer’s contracting party | What the website must show |
|---|---|---|
| Each firm on its own | each firm for its own trade, with its own quote and its own invoice | three providers, a clear owner for every trade page, a note that contracts are separate |
| Lead firm | one firm as contractor, the others work for it | who the contracting party is and which partners carry out the work |
| Joint company | the company, for example a GbR or a GmbH | the company with all details, plus the participating firms |
The first model is the simplest: the website bundles the appearance, the contracts stay separate. Each firm writes its own quote, invoices on its own and is liable for its own work. In the second model, one firm takes overall responsibility towards the customer and engages the others. Whether a firm may offer work in a trade for which it is not registered itself is a question for the chamber of skilled trades, not for the website.
The third model sometimes arises without anyone deciding on it. A civil-law partnership (GbR) needs neither a notary nor a register entry. If the purpose of the partnership is to run a business under a common name, it is presumed to take part in legal transactions, that is, to enter into contracts itself (§ 705(3) BGB). The partners are personally liable to creditors for its obligations as joint and several debtors (§ 721 BGB). A common name, a joint offer and a website that only ever says “we” can add to that picture. Anyone who wants separate contracts therefore says so explicitly on the site, preferably on the home page and on the process page.
Then there is the Trade and Crafts Code. All three trades in the example require a license: painters and varnishers are listed as no. 10, plumbers and heating fitters as no. 24 and electrical technicians as no. 25 in Schedule A, which lists 53 trades in total (Schedule A HwO). Only persons and companies entered in the register of skilled trades may run a licensed trade independently, explicitly including civil-law partnerships (§ 1(1) HwO). If the cooperation itself acts as provider, the question of its registration belongs with the chamber of skilled trades before the website goes live.
Competition law looks at the contracting party as well. If services are offered with a price in a way that lets an average consumer conclude the deal, the identity and address of the trader count as material information, where applicable also those of the trader on whose behalf he acts (§ 5b(1) no. 2 UWG). A cooperation site that names a fixed price for a complete bathroom therefore says right next to the price who is making the offer.
Not legal advice, but a working aid
The structure: one roof, one page per trade
Once the model is settled, the structure follows. It has two jobs that seem to contradict each other at first glance: the site should feel like an offer from a single source, and at every point it should make clear which firm is speaking. A structure with a shared home page, a separate page for each trade and a page describing the joint process usually works well.
Shared home page
What the firms offer together, such as bathroom or old-building renovation, for which area, and three clearly labeled routes to the trades. The cooperation’s name sits at the top, the participating firms below it.
Electrical page
The electrical firm’s part in the joint project, its name in the first paragraph, master craftsperson and contact, its own reference photos and a link to the firm’s own website.
Plumbing and heating page
The same pattern for the plumbing and heating firm: bathroom, pipework, heating, with its own form recipient and a note on who is the contracting party for this work.
Painting page
Walls, ceilings and surfaces once plumbing and electrical work are done, with the painting firm named as provider and its own photos instead of shared stock images.
Process of joint projects
In which order the trades arrive, who coordinates the dates, who acts as the customer’s fixed contact and which invoice comes from whom.
Request with choice of trade
A form in which customers tick the trades they need. Each request goes only to the firms selected, and the confirmation of receipt names them.
Each trade page names the firm doing the work not just in the legal notice but in the page header and the first paragraph. That helps customers, and it makes the assignment unambiguous on which the legal notice and the privacy notice later rely. How a single service page is built is described in the article on service pages instead of one combined page; the same applies to a cooperation site, with the firm’s name as an additional mandatory line.
The addresses follow the structure: a home page, below it one address per trade such as /elektro/, /sanitaer-heizung/ and /maler/, plus /ablauf/, /anfrage/, /impressum/ and /datenschutz/. The menu stays the same on every page. Anyone who lands on the painting page from a search reaches the other two trades and the joint form in one step. Home page, three trade pages, process and request make six pages, and with the legal notice and the privacy notice eight.
A common question is whether every trade page needs its own design. Usually not. A shared design with the cooperation’s color and mark works better than three logos competing for attention. The firms appear by name and, where they want, with a small version of their mark on their trade page. What pages for individual trades can look like is shown on our pages on web design for electrical contractors, for plumbing and heating and for painters and decorators.
Cooperation site and own website side by side
The cooperation site rarely stands alone. 94 percent (Bitkom 2025) of the trade businesses surveyed use a website of their own; the survey covered 504 trade businesses (Bitkom 2025) in Germany, from small firms to larger trade companies. As a rule, the three partners therefore bring three existing websites with them. That has consequences for texts, links, business details and the domain.
Texts: copying the service description from your own website into the cooperation’s trade page creates two almost identical pages at two addresses. If nobody specifies a preferred version, Google itself chooses which version it shows to users of its search (Google Search Central). That need not be the page the firm wants to see in the results. A clear division of work is better: the firm’s own website describes its whole offer, the cooperation’s trade page only its part in the joint project.
Links: every trade page links to the firm’s website, and every firm’s website mentions the cooperation with a link to the shared home page. That way customers see on both routes who is behind it, and a firm does not lose requests to the joint site that it would rather receive directly.
Business details: a firm’s name, address and phone number appear on the cooperation site exactly as on its own website, in the legal notice and in its business profile. Differing spellings cost trust and correct assignment; what matters here is explained in the article on consistent business details. Each firm keeps its own Google business profile.
Domain: the shared address belongs to someone, even if everyone uses it. Who registers it, who holds the access details and what happens to it when the cooperation ends should be agreed in writing before launch. The questions are the same as for a single firm, only with three parties; they are covered in the article on domain and hosting.
How requests reach the right firm
The form is where day-to-day use shows whether a cooperation site works. A request for a new bathroom often concerns all three trades, a request for an extra socket only one. Three approaches are common:
- One form per trade page: each trade page has its own form that goes straight to the firm. Simple and unambiguous, but awkward for customers who need several trades.
- One form with a choice of trade: customers tick the trades they need. The form sends the request to exactly those firms and names them in the confirmation of receipt. For most cooperations this is the approach that holds up.
- Central intake: one firm or a shared office takes all requests and distributes them. That spares the customer effort but requires a clear rule on whose behalf the receiving party acts.
Handling a request does not require consent: it is necessary to take steps at the request of the data subject prior to entering into a contract (Art. 6(1)(b) GDPR). But that basis only reaches as far as the request itself. Someone who asked the electrician has not asked the painter. The German data protection conference states that passing data between joint controllers is a processing operation of its own that needs its own legal basis (DSK, Kurzpapier Nr. 16). The choice of trade in the form solves this cleanly: customers decide themselves who receives their request.
A shared inbox in which all three firms read every request is convenient and still the weaker solution. Personal data should be limited to what is necessary for the purposes of the processing (Art. 5(1)(c) GDPR). A request that does not concern a firm does not belong in its inbox.
Choose trades
The customer ticks electrical and plumbing, describes the project and uploads photos if needed. Only a way to reach her, the location and at least one trade are mandatory.
Route
The form sends the request to the two firms selected, not to the third. Each email carries a subject line with trade and location so it can be assigned in the firm at once.
Confirm
The confirmation of receipt to the customer names the firms that received the request and who will get in touch first. That way she knows who has her details.
Coordinate
In joint projects, the agreed contact person coordinates the dates. Whether that person sees the other firms’ details for this is set out in the firms’ arrangement.
The customer ticks electrical and plumbing, describes the project and uploads photos if needed. Only a way to reach her, the location and at least one trade are mandatory.
The form sends the request to the two firms selected, not to the third. Each email carries a subject line with trade and location so it can be assigned in the firm at once.
The confirmation of receipt to the customer names the firms that received the request and who will get in touch first. That way she knows who has her details.
In joint projects, the agreed contact person coordinates the dates. Whether that person sees the other firms’ details for this is set out in the firms’ arrangement.
Technically this means: the form knows one recipient address per trade, and a change to that list is a logged step, not a quick fix. If the emails go to three different domains, each of them has to accept mail from the website; why form emails otherwise end up in spam is explained in the article on form emails landing in spam. Which fields the form itself needs is covered in the article on the request form for trade businesses.
The legal notice: every firm with complete details
The duty to identify the provider applies to service providers for digital services offered on a business basis, usually for payment. The details must be easy to recognize, directly accessible and permanently available (§ 5(1) DDG). A service provider is whoever offers the digital service (§ 1(4) no. 5 DDG). On a cooperation site, that is not automatically just one firm. If every firm offers its own services on the site, there is much to be said for naming all three in full. A superfluous line does less harm than a missing one.
For each firm this includes: name and address of the establishment, for legal entities also legal form and authorized representatives (§ 5(1) no. 1 DDG); details allowing fast electronic contact, including the email address (§ 5(1) no. 2 DDG); the register and the registration number if the firm is registered (§ 5(1) no. 4 DDG); for licensed trades, as a rule, the chamber, the statutory professional title with the state in which it was awarded, and the professional rules (§ 5(1) no. 5 DDG); and the VAT identification number if the firm has one (§ 5(1) no. 6 DDG). What that means for a single trade business is set out in detail in the article on the legal notice and privacy.
The three blocks rarely look alike. Of the businesses in licensed and non-licensed trades covered by the census of skilled trades, 67.5 percent are sole traders, 24.2 percent GmbHs and 7.9 percent partnerships (ZDH, Handwerkszählung 2024). A GmbH often stands next to two sole traders. For a sole trader the block carries the owner’s name, for a GmbH the legal form, the management and the commercial register number.
| Detail | Sole trader | GmbH | Registered GbR |
|---|---|---|---|
| Name | first and last name, a business name only in addition | company name with the suffix GmbH | name with the suffix eGbR |
| Representation | the owner in person | managing director | partners authorized to represent |
| Register | commercial register only if registered | commercial register with court and number | register of civil-law partnerships with court and number |
| Chamber and title | chamber of skilled trades, professional title, state | the same details for the firm | the same details if the company itself is registered |
| Contact | address, email, phone | address, email, phone | address, email, phone |
If the cooperation itself is a GbR entered in the register of civil-law partnerships, it carries the name suffix “eingetragene Gesellschaft bürgerlichen Rechts” or “eGbR” (§ 707a(2) BGB) and appears in the legal notice with register and number. The participating firms still belong on the page if they appear there with their own services.
On the layout of the legal notice page: a short sentence at the top explains who runs the website and which firm stands behind which trade page. The blocks follow below, each firm under its own heading. The link to the legal notice sits in the footer of every page, including the trade pages. Anyone who intentionally or negligently fails to make the details available, or makes them available incorrectly or incompletely, commits an administrative offense that can be punished with a fine of up to 50,000 euros (§ 33 DDG).
Data protection: who the controller is
The controller is whoever, alone or jointly with others, determines the purposes and means of the processing of personal data (Art. 4(7) GDPR). Where two or more controllers jointly determine purposes and means, they are joint controllers (Art. 26(1) GDPR). On a cooperation site that is precisely the normal case: the firms decide together that there is a website and a form, which fields it has and where the details go.
That does not mean that all three are equally responsible for everything. The German data protection conference writes that the existence of joint responsibility does not necessarily mean equal responsibility (DSK, Kurzpapier Nr. 16). It also describes the case that comes closest to a cooperation site: participants can be separately responsible for individual parts or phases of a processing operation while the data are brought together via a shared platform; the joint processing is then limited to running the platform (DSK, Kurzpapier Nr. 16).
Applied to the example: the three firms are jointly responsible for the website, the form and the routing of requests. What the plumbing firm does with a request once it has arrived is its responsibility alone: quote, appointment, order, retention. If, on the other hand, a joint company runs the site and receives the requests itself, it is the more likely controller.
Whoever hosts or maintains the website and has access to form data in the process is usually a processor. Processing by a processor is governed by a contract that sets out the subject matter and duration, nature and purpose of the processing and the obligations and rights of the controller (Art. 28(3) GDPR). With three controllers this means: either all three are party to the contract, or the firms agree among themselves who concludes it with effect for all.
When the data are collected, the privacy notice states the identity and contact details of the controller (Art. 13(1)(a) GDPR), here of all participating firms. It describes which details the form collects, to whom it sends them and which firm is responsible for what. For everything else, such as content from third-party servers or statistics, the same rules apply as on any other website.
What belongs in the arrangement under Article 26
Joint controllers determine in a transparent arrangement which of them fulfills which obligation, in particular regarding the rights of data subjects and the information duties (Art. 26(1) GDPR). The essence of the arrangement is made available to the data subject (Art. 26(2) GDPR). In the view of the German data protection conference it should in principle be sufficient to provide these essential elements on a website (DSK, Kurzpapier Nr. 16). For a cooperation, a separate section in the privacy notice is the obvious place. The arrangement itself should cover at least these points:
- Roles: who runs the website, who manages the form and which firm receives which requests.
- Contact point: whom data subjects should contact; the arrangement may designate a contact point for them (Art. 26(1) GDPR).
- Access and erasure: who answers requests. The deadline is one month from receipt (Art. 12(3) GDPR) and may be extended by two further months where the complexity and number of requests make it necessary (Art. 12(3) GDPR).
- Data breach: who notifies a personal data breach, without undue delay and, where feasible, within 72 hours of becoming aware of it (Art. 33(1) GDPR).
- Service providers: who concludes the processing contract with hosting and maintenance and who approves changes to the form and the list of recipients.
- Deletion periods: when requests that did not lead to an order are deleted and who takes care of it, separately for each firm.
- Exit: what happens to requests, access details and the trade page when a firm leaves the cooperation.
The division of tasks binds the firms among themselves, not the customers. Irrespective of the terms of the arrangement, the data subject may exercise his or her rights in respect of and against each of the controllers (Art. 26(3) GDPR). If a customer writes to the painting firm asking it to delete her data although she only contacted the electrical firm, the painting firm must know to whom it passes the request and who tracks the deadline.
One contact point, three responsibilities
The arrangement is not a form you fill in once and forget. The German data protection conference points out that fines can be imposed where joint responsibility exists without an arrangement under Art. 26 having been concluded (DSK, Kurzpapier Nr. 16). When the cooperation changes, the arrangement changes with it.
When a firm leaves or a trade joins
Cooperations change. A firm is handed over to a successor, a tiler joins, a partner goes its own way. On the website, four places are affected, and on the same day: the trade page, the legal notice, the form’s list of recipients and the privacy notice.
If a firm leaves, its trade page is removed or redirected to its own website so that links and search results do not lead nowhere. Its block disappears from the legal notice, its address from the form, its name from the privacy notice. What happens to requests that are with it is settled by the arrangement.
If a firm joins, the reverse applies: it comes in for future requests, not past ones. According to the German data protection conference, nobody can join an existing processing operation for the past; further controllers can join for the future (DSK, Kurzpapier Nr. 16). Old requests to the cooperation therefore do not belong in its inbox. The new trade page follows the pattern of the others, and the home page names the new partner as well.
The order of steps before launch
- Put the contract model in writing: who is the customer’s contracting party, who writes the quote and who is liable.
- Check with the chamber of skilled trades whether the cooperation itself must be registered if it acts as provider.
- Conclude the arrangement under Art. 26 GDPR, together with the contract for hosting and maintenance.
- Settle the page plan and the texts for each firm, without copies from the firms’ own websites.
- Set up the form with a choice of trade and test it with one test request to each firm.
- Have every firm proofread the legal notice and the privacy notice, then publish and link from the firms’ own websites.
The firms handle the first three steps among themselves; the last three can be carried out with the agency. Anyone who starts with the website and clarifies the roles later usually builds the site twice: once the way it should look and once the way the contracts require.
What it costs to set up
A cooperation site with a shared home page, three trade pages, process, request, legal notice and privacy notice has eight pages. We build a website for trade businesses for a fixed price from 1,490 euros net with up to eight pages, including the request form, legal notice and privacy information. Who the client is, one firm on behalf of all or the joint company, we set out beforehand in the quote. Ongoing maintenance costs from 49 euros per month, hosting in Germany from 15 euros per month, both cancelable monthly, with no minimum term; what maintenance includes is described under maintenance and support. All prices, as of September 2026, are on the pricing page.
The part no agency can take over is done by the firms: the contract model, the arrangement among themselves and the details for the three blocks in the legal notice. We make sure the site shows these decisions and that the form sends each request where it belongs. If a cost estimate is given via the website in a joint project, what applies is set out in the article on the cost estimate under § 649 BGB. Our other services are listed under services; you can arrange a first conversation via contact.
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Cost estimates on a trade website: what § 649 BGB means
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