Quick answer
In 2026, a tax advisor's own client portal can typically be built with no-code/low-code tools (Softr for the frontend, Make or n8n for automation) in 4–8 weeks, for a one-off build cost of €6,000–€20,000 plus €50–€250 in running costs per month. Rented off-the-shelf software (DATEV Meine Steuern, portals from Addison or specialised SaaS vendors) launches faster, but costs you on an ongoing per-user, per-month basis and can barely be adapted to your own processes. The rule of thumb: rent if you want to mirror a standard process one-to-one — build your own if the portal, onboarding and workflows are meant to be your differentiator and ownership of data and processes matters to you.
What a client portal must do
A client portal is the digital interface between the firm and the client. Core features that count as standard in 2026:
- Secure document exchange (receipts, tax assessments, annual accounts) instead of email attachments
- Status overview per engagement („Your tax return is in progress / approved / filed“)
- Task and request management („Please submit the following documents“)
- Deadline and appointment overview
- Invoices and payment status
- Roles and permissions (client, bookkeeper, advisor, firm management)
On top of that, AI-assisted features are increasingly common in 2026: automatic document classification, pre-filled checklists, and a portal chatbot that answers standard questions („Where is my tax assessment?“) without a staff member having to respond.
Build vs. buy: the honest decision matrix
When renting off-the-shelf software makes sense
- You want to start immediately and have no IT resources.
- Your processes are DATEV-centric and you already use the DATEV ecosystem deeply.
- You accept that all your clients see the same portal as at a thousand other firms.
- Your firm has fewer than 300 active engagements and user licences remain manageable.
When your own portal is the better choice
- You want a branded portal (logo, domain, look & feel) that reinforces your positioning.
- Your processes deviate from the standard — e.g. specialised sectors (doctors, hospitality, influencers) with their own checklists.
- You are scaling to hundreds of clients and the per-user rental costs add up faster than building your own.
- You want to keep data in your own systems (Airtable, Postgres, your own CRM) and process it flexibly.
- You want to interlock the portal with your own offering (advisory packages, onboarding, upsells).
The decisive difference is ownership. A rented portal ends when the subscription ends — processes, data and custom logic stay with the vendor. A self-built portal on open tools belongs to your firm; you can extend, migrate and export it.
The no-code stack for your own client portal (2026)
For tax firms in the DACH region, a proven stack has emerged that works without classic software development:
Frontend: Softr
Softr delivers the actual portal — login, client dashboards, document lists, forms and role-based views. Softr connects directly to a database (Airtable, Google Sheets or a SQL source) and renders protected user areas from it. Advantages: GDPR-compliant hosting options in the EU, granular access rights per client, individual branding on your own domain.
Database: Airtable or Postgres
The database is the backbone: client master data, engagement status, document metadata, tasks. For smaller firms Airtable is enough; from several thousand records and higher compliance requirements onwards, a self-hosted Postgres database (EU server) makes sense.
Automation: Make and n8n
Make and n8n are the automation brain. They connect the portal, database, email, DATEV interfaces and AI services. Typical automations:
- New document uploaded → notification to the responsible clerk
- Deadline approaching → automatic reminder to the client
- Status “filed” → email confirmation with a summary
- Missing document → automatic follow-up sequence
n8n can be self-hosted (full data sovereignty, EU servers), Make scores with faster setup and a broad app library. Many firms use both in combination.
AI layer (optional, increasingly standard in 2026)
A connected language model handles document classification, extracts invoice data and answers client questions in the portal. Important: processing via EU-hosted services or services covered by a data processing agreement, and no clear-text data sent to unregulated models.
Cost comparison (as of 2026)
| Cost factor | Off-the-shelf software (rent) | Your own portal (Softr/Make/n8n) |
|---|---|---|
| Setup / build | €0–€2,000 | €6,000–€20,000 one-off |
| Ongoing | Per user/month, often €5–€20 per client | €50–€250/month (tool subscriptions, hosting) |
| Adaptability | Low (vendor roadmap) | High (your own processes) |
| Data sovereignty | With the vendor | With the firm |
| Time to live | Days | 4–8 weeks |
The maths tips in favour of building as soon as the number of client users grows: a portal with 500 clients quickly costs €5,000/month in rent at €10 per user per month — a self-built portal, by contrast, scales with almost no marginal cost per user.
Six steps to your own client portal
- 1Map your processes. Which interactions currently run via email and phone? Document exchange, status enquiries, deadlines? That list is your requirements catalogue.
- 2Define the data model. Tables for clients, engagements, documents, tasks and deadlines — including their relationships. The data model determines your flexibility later on.
- 3Build the frontend in Softr. Role-based dashboards: the client sees only their data, the clerk sees their portfolio, firm management sees everything.
- 4Wire up automations in Make/n8n. Notifications, reminders, follow-up logic and the connection to existing systems.
- 5Secure it and cover GDPR. EU hosting, encrypted transmission, data processing agreements (DPAs) with all tool vendors, a deletion policy, two-factor login.
- 6Pilot with 10–20 clients. Collect feedback, refine, then roll out.
Connecting DATEV and existing systems
Your own portal does not have to replace DATEV — it complements it as a client frontend. Via interfaces (DATEVconnect / DATEV API, CSV/DUO exports or middleware), documents and status data can be synchronised between DATEV and the portal. In practice this means: your staff keep working in DATEV, while clients use the lean, branded portal. Make and n8n act as the bridge, so no duplicate data maintenance arises.
A clean architecture is key: DATEV remains the „system of record“ for tax processing, the portal is the „system of engagement“ for client communication. That way you avoid conflicts and data silos.
GDPR and professional law: what tax firms must observe
Tax advisors are bound by professional confidentiality (§ 203 of the German Criminal Code) and the GDPR. For your own portal, that means concretely:
- EU hosting for database and automation (self-hosted n8n on German/EU servers is ideal here).
- A DPA with every service provider you use (Softr, Make, hosting).
- Access control: role-based permissions, two-factor authentication, logging.
- A deletion policy in line with retention periods.
- For AI features: no client-related clear-text data sent to models without a DPA and EU processing.
The advantage of building your own: you retain full control over the data flow and can deliberately choose a stack that is clean under professional and data protection law.
Common mistakes when building your own
- Too much at once. Start with document exchange and status — not with 30 features.
- No data model. Starting without a well-thought-out table structure builds in technical debt.
- No clear ownership. An internal or external team has to maintain and evolve the portal.
- Security as an afterthought. GDPR and the permission concept belong in step 1, not retrofitted later.
FAQ
How long does it take to build your own client portal?
A working portal with login, document exchange, status overview and basic automations is usually live in 4–8 weeks with the Softr/Make/n8n stack. A pilot with a few clients can start after just 2–3 weeks.
Is a no-code portal GDPR-compliant for tax firms?
Yes, provided EU hosting, data processing agreements, encrypted transmission, a permission concept and a deletion policy are in place. Self-hosted n8n on EU servers gives maximum data sovereignty. Professional confidentiality can be maintained with clean access control.
Is building your own worth it for small firms?
Below roughly 100 engagements and with standard processes, rented software is often faster and cheaper. As the number of clients grows, with a specialised focus, or when you want a branded portal, building your own becomes economically and strategically more attractive.
Does the portal replace my DATEV environment?
No. The portal is the client frontend; DATEV remains the leading system for tax processing. The two are connected via interfaces and automation (Make/n8n), so no duplicate data entry arises.
Who owns the portal if an agency builds it?
In a cleanly run project, the database, accounts and configuration belong to your firm. That is precisely the core advantage over rented software: you own the system and can switch vendor or service provider at any time.
Conclusion
In 2026, building your own client portal as a tax advisor is no longer a major IT investment, but a plannable no-code project with a clear ROI beyond a certain number of clients. Those who want to own their processes, brand and data build — those who just want to map a standard process quickly rent. Mindflows builds such portals on Softr, Make and n8n for firms in the DACH region — GDPR-compliant, DATEV-ready and owned by the client.