Custom Kadaster integration development
Appfront builds custom Kadaster integrations for notaries, estate agents, mortgage lenders and municipalities. Using the official BAG, BRK and KLIC APIs, your application retrieves real-time address, parcel and ownership data: securely, scalably and with complete audit logs.
What is a Kadaster integration?
The Kadaster (Dutch Land Registry) manages the Key Registers of Addresses and Buildings (BAG) and Land Registry (BRK), the KLIC notification chain for excavation work, and a growing number of OGC-compliant geoservices. A Kadaster integration is the technical link that lets your application communicate directly with these registers, without manual steps in Mijn Kadaster.
In practice, a good integration replaces manual lookups in Mijn Kadaster or BRK Online with an API call that returns the right data within a few hundred milliseconds: a verified address, cadastral designation, ownership information or a KLIC excavation notification. That saves minutes per transaction, which adds up quickly for notaries, valuation firms and municipalities.
Appfront builds these integrations to measure. We align with the official specifications, handle certification and authorisation via Mijn Kadaster and eHerkenning, and make sure your application copes cleanly with version changes in the underlying APIs (BAG versions, BRK extensions, KLIC WIBON updates).
Which Kadaster APIs do we integrate?
Appfront works routinely with the full Kadaster API portfolio. For each project we select the combination that suits your use case, from a light BAG query to a complete BRK delivery process.
BAG API Individual Queries
Real-time querying of residential objects, buildings, mooring places and stand places. Includes the current postcode table, status (in use / not in use / demolished), floor area, construction year and intended use.
BAG WFS / WMS
Geo-services for BAG objects: retrieving geometries, buildings within an area, or displaying them on your own map in a dashboard or inspection app.
BRK Queries
Synchronous querying of cadastral objects and legal entities holding rights. For notaries and valuation firms, the basis for research, case preparation and ownership checks.
BRK Delivery
Bulk or mutation deliveries of BRK data, used by high-volume users such as banks, municipal case management systems and RES organisations that need a continuously up-to-date picture.
KLIC (WIBON)
Submitting excavation notifications, receiving KLIC files and handling the Precautionary Measures Requirement process. Essential for network operators, contractors and groundworkers.
BRK Notifications
Push notifications on changes to a monitored parcel or legal entity holding rights, crucial for banks that want to proactively monitor mortgage files.
If you dig yourself, you also have your own obligation: the excavation notification, which is valid for a few weeks. See WIBON software.
Who do we build Kadaster integrations for?
How you use the Kadaster differs greatly by sector. Our integrations are always built around a concrete business process, not a generic API wrapper.
If you want ownership and rights per parcel from the Basic Registry Land Registry in your own system, see our page on a BRK integration.
If you want to use the Basic Registry Topography as a map or as data, see our page on a BRT integration.
Notaries
Full deed automation: a file opens with BAG address validation, is populated with BRK Bevragen data on legal owners, and is filled in field by field with verified information.
- Search report for every new deed
- Automatic checks for seizures and mortgages
- Integration with appointment planners and KIK-Inzage
Estate agents & valuation
Property capture flows that directly retrieve cadastral designation, surface area and ownership status. Valuation applications enrich themselves with BRK data so that reference properties are suggested automatically.
- Address validation in online sales forms
- Construction year and floor area from BAG IB
- Recent sales data via BRK Levering
Banks & mortgage lenders
Acceptance processes that check in real time whether the collateral to be financed exists (BAG), who owns it (BRK), and whether any existing security rights rest on it. BRK Notificaties monitors the portfolio.
- Collateral validation during mortgage applications
- Continuous monitoring of mortgage borrowers
- Compliance audit trail for DNB
Municipalities & case management systems
BAG integrations with case management systems, permit workflows and citizen portals. Objection procedures for WOZ property valuations, environmental permits and enforcement all rely on accurate address and building information.
- BAG validation in case management systems (Centric, Roxit, Civision)
- Geo-services in citizen portal maps
- Mutation subscriptions for BRP integrations
Grid operators & contractors
KLIC flows for excavation work: submitting notifications, retrieving cable and pipeline PDFs and GeoJSON files, and handling the EV process from the work preparation system.
- Integrated KLIC notifications from project software
- Automatic archiving of KLIC deliveries
- Groundworker app on tablet for field staff
PropTech & SaaS builders
SaaS platforms that want to offer their end users cadastral information, from sustainability platforms and rental management software to data vendors. We handle usage limits, throttling and cost control.
- Multi-tenant Kadaster access via one subscription
- Caching layer for high volumes of BAG queries
- Passing on Kadaster fees to end customers
Our development process for Kadaster integrations
A Kadaster integration touches certificate management, legal licences and sensitive personal data. We work in four phases to prevent unexpected issues from surfacing only at go-live.
API selection & licence check
We determine which products you need (BAG, BRK Bevragen, BRK Levering, KLIC, BRK Notificaties) and check your Mijn Kadaster roles, subscriptions and certificate status.
Architecture & security
We design mTLS, the eHerkenning flow, error handling and caching strategy. For personal data, we record the data processing agreement and the processing register straight away.
Build & acceptance environment
Implementation against the Kadaster acceptance environment, with automated tests, contract tests and structured logging. Demonstrable builds along the way.
Go-live & management
Controlled transition to production, certificate calendar set up, monitoring of API quotas and latency, and ongoing management around Kadaster version changes.
What goes into a properly built Kadaster integration?
mTLS + PKIoverheid
Mutual TLS with PKIoverheid services server certificates. Automated rotation via Vault or similar secret stores, with alerts well ahead of the expiry date.
eHerkenning EH3+ flows
For BRK queries that natural persons are permitted to see, we handle the eHerkenning integration via an authorised estate agent, including mandate management in Mijn Kadaster.
Cache & idempotency
BAG queries can often be cached; BRK queries usually cannot. We build a cache policy per API that matches your legal and operational requirements.
Audit & logging
Complete audit logs of who queried what and when, in line with the requirements of the Kadaster and your own processing register. Logs are searchable for compliance audits.
Rate limiting & quotas
Kadaster APIs have hard per-minute quotas. We build client-side rate limiters, fair queuing between tenants, and alerts for when you approach a limit.
Versioning strategy
BAG and BRK receive new versions periodically. We put contract tests in place so you can see in good time when a schema migration is needed, and are never caught off guard by a breaking change.
What does the implementation look like?
The integration layer typically runs as a separate service in your architecture, in Node.js, Python, .NET or Laravel, depending on your existing stack. We keep business logic (for example, "validate address on entry") separate from the Kadaster call, so you are not locked into one implementation.
For high-volume clients we build a dedicated caching proxy using Redis or CDN edge caching, so repeated BAG queries from end users do not each incur a production call to the Kadaster.
The integration is delivered with a runbook (what to do when a certificate expires, how to add a new Mijn Kadaster role, how to manually redeliver a KLIC file) so your own team can take ownership.
Example stack
Backend
Node.js + Fastify, Python + FastAPI, or .NET 8 Web API. All with OpenTelemetry for traces.
Authentication
PKIoverheid certificate via HashiCorp Vault, eHerkenning via an authorised broker (Connectis, Digidentity, Reconi).
Cache & queue
Redis for the BAG cache, RabbitMQ or AWS SQS for KLIC jobs and bulk deliveries.
Monitoring
Grafana + Prometheus, with alerts on latency, error rate and certificate expiry date.
Frequently asked questions about Kadaster integrations
What is a Kadaster integration?
A Kadaster integration is a technical link between your application and the official Kadaster APIs (BAG, BRK, KLIC). It lets you retrieve real-time address, parcel and ownership data, or send excavation notifications to the Kadaster automatically, without manual steps in Mijn Kadaster.
Which Kadaster APIs do you use most often?
For address validation and BAG queries we deploy the BAG API Individual Queries. For ownership and cadastral information we use BRK Bevragen and BRK Levering. For excavation work we integrate with KLIC. We also work with OGC-compliant WFS and WMS services for geo-visualisations.
Which authentication and certificates are required?
Production Kadaster APIs require a PKIoverheid services server certificate plus an activated Mijn Kadaster account. Some BRK services additionally require eHerkenning level EH3 or higher. We guide you through the certificate application, the setup of Mijn Kadaster roles and the mTLS configuration on the application side.
How much does querying the Kadaster cost?
The Kadaster charges a tariff per product (BAG, BRK Query, BRK Delivery, KLIC). Usage costs are separate from the implementation cost of the integration. We design the architecture so you only pay for necessary queries, using caching and idempotency strategies where the use case allows.
For which organisations do you build Kadaster integrations?
We work with civil-law notaries (deed automation, file enrichment), estate agents (property capture, cadastral searches), banks and mortgage lenders (acceptance and valuation processes), construction firms and grid operators (KLIC notifications), and municipalities and RES organisations (BAG integrations with case management systems).
How do you handle the sensitivity of ownership data?
BRK data is personal data and falls under the GDPR. We apply data minimisation (retrieving only the fields strictly necessary), encryption in transit (mTLS) and at rest, role-based access, and logging that meets the Kadaster's requirements. We also help draft the data processing agreement and the record of processing activities.
Can you also take over an existing Kadaster integration?
Yes. We carry out a code and architecture review, check the certificate chain, review the Kadaster licences and role assignments in Mijn Kadaster, and then put together a maintenance plan. After that we handle monitoring, certificate renewal, schema migrations (for example when BAG versions change) and extensions.
Want to start a project?
We'd love to hear from you.
Got a lot to say, or did you send it another way by email? Choose Detailed brief: headings and bullet points, images in the text and files attached.
We've received your brief
We'll read through it and usually reply within one working day. Have anything to add? Send it to fabian.vandijk@appfront.nl.
Your message has been sent
Thank you for your interest! We'll get back to you as soon as possible, usually within 1 working day.
Let's get started
Together, we create smart digital solutions for your organisation's challenges. Not rushed, short-lived products, but thoughtful, high-quality solutions built on a foundation of UX design and technological expertise, so your organisation is ready for tomorrow.
Or explore our case studies, blog posts or get to know our team.