Getting started with SnelStart

This guide is for you, the Apideck customer building an integration on the SnelStart B2B API. It covers applying for API access, getting a free development subscription so you can build immediately, certifying your integration, and configuring the resulting credentials in Apideck.

The maatwerkkoppeling flow this connector uses does not use OAuth. Access rests on two separate credentials, and the split matters because it decides who has to supply what:

Credential	Who holds it	Where it goes
Ocp-Apim-Subscription-Key (Subscription Key)	You, the application owner — one key for your whole integration	The Apideck connector configuration. Never collected from a consumer.
Connection Key (maatwerksleutel)	Each consumer generates their own, in their own SnelStart account, scoped to a single administration	Vault, on the consumer's own connection

Apideck handles the rest: the Connection Key is exchanged for a short-lived access token at https://auth.snelstart.nl/b2b/token on every request (roughly a 60-minute lifetime, cached and refreshed for you), so there is no token flow for you to build.

Before you start

A SnelStart subscription on the inZicht or inControle package. The custom-connection (Maatwerk) area that issues a Connection Key is only available on those two packages — inStap, inKaart, inBalans and inOrde do not expose API or custom-connection access. This applies to every SnelStart account that will connect, so it is worth confirming with a consumer early.
An Apideck account with the SnelStart connector available under Configuration → Accounting → SnelStart.
A heads-up on the documentation. SnelStart's B2B API reference is auto-generated, lives entirely inside the Developer Portal (visible only after you sign in), and is Dutch-only. Plan a translation pass over the endpoint descriptions if nobody on the team reads Dutch — the resource names are shared with the rest of the accounting domain, so that is usually enough.

1. Apply for API access

Submit the API integration application form linked from snelstart.nl/api (direct link: API-koppeling aanvragen).

The form asks which kind of integration you are building. SnelStart distinguishes two:

Maatwerkkoppeling (custom integration) — built for one specific end customer. This is the flow the Apideck SnelStart connector uses today: each connection is authorized by a consumer-supplied maatwerksleutel.
Productiekoppeling (production integration) — built to serve many end users. This is a different authentication model, not a larger version of the maatwerk one: SnelStart requires the OAuth authorization-code flow for a productiekoppeling, plus a registered webhook URL on the application form. The Apideck SnelStart connector authenticates with a custom grant_type=clientkey token exchange rather than OAuth, so it is structurally maatwerkkoppeling-only. Going the productiekoppeling route means building and certifying a second, OAuth-based integration alongside this one — it is not a paperwork change on the existing one.

SnelStart reviews every application individually and is deliberately selective about admitting new production integrations, so make the application concrete: name the end customer, the administration(s) involved, and the resources you need to read and write. SnelStart publishes no figure for how long this first review takes, so ask your SnelStart contact for an expected timeline once you have submitted.

Developer and API questions go to partner@snelstart.nl.

2. Register on the Developer Portal and start building right away

You do not have to wait for the certification decision to begin. Create a free account on the SnelStart B2B API Developer Portal and subscribe to the Ontwikkeling & Test (Development & Test) product. That issues a temporary development Subscription Key you can build and test against immediately, and unlocks the API reference documentation.

The development key is bounded in two independent ways, and either one can end your access:

It is valid for 90 days from issue.
It is limited in the number of API calls it may make — a hard cap on request count, on top of the time window. A heavy test-data backfill or a long-running polling loop can exhaust the quota well before the 90 days are up, so pace your test traffic and keep an eye on it.

Aim to finish the build and submit your certification application inside that window. If you need longer, raise it with partner@snelstart.nl.

Keep an active product on your portal account. A Developer Portal account with no active product — meaning no subscription key — is automatically deleted after 1 day. If your Ontwikkeling & Test key lapses (90 days elapsed, or the call quota exhausted), recreate it within one day or the account is deleted along with it. This is recoverable: SnelStart allows re-registering with the same email address. But you lose the account and start the portal setup over, so it is worth a calendar reminder — particularly if you pause the build between the development phase and certification.

3. Configure your Subscription Key in Apideck

Open the Apideck SnelStart connector settings and paste the key from the Developer Portal into the Subscription Key field, then save.

Two things to keep straight:

The Subscription Key is integration-level. One key covers every consumer connection on this connector — you set it once, and it is not part of the consumer's connect flow. Requests that reach SnelStart without it are rejected at the API gateway before any authentication happens.
The Connection Key is the consumer's to create and paste into Vault. Point consumers at the connection guide rather than asking them for a Subscription Key or handing them yours.

Start with the temporary development key here; swap in the permanent one after certification (step 5).

4. Apply for certification

Once your integration works against the development subscription, apply for certification using the form at snelstart.nl/api/certificeren. The form asks for details about the integration and the coupling itself.

A certification and monitoring period follows, during which SnelStart observes your integration's actual API traffic — so keep the integration running and exercising the endpoints it needs after you submit. SnelStart describes this period as roughly 12 days; treat that as its own indicative figure rather than a commitment, and confirm the status of your own application with your SnelStart contact. The outcome is either an approved integration with a permanent key issued, or a rejection, in which case SnelStart contacts the developer directly.

5. Swap in your permanent Subscription Key

Approval issues one credential to you: a permanent Ocp-Apim-Subscription-Key, at the Custom Integration (Maatwerk) tier for this connector's flow (the equivalent for a productiekoppeling is a productiesleutel). Both names describe a subscription-key tier, so do not read them as a consumer credential: the Connection Key each consumer pastes into Vault is generated by that consumer in their own SnelStart account and is never issued to you or by you.

A one-time fee is invoiced when the permanent key is issued — see the Overview tab for the exact amount.

Then:

Replace the development key in the Subscription Key field of the Apideck connector settings with the permanent Ocp-Apim-Subscription-Key.
Nothing changes for your consumers. Each one continues to generate their own Connection Key in SnelStart and paste it into Vault — send them to the connection guide for that.

FAQ and troubleshooting

Every request fails before authentication, on all resources. Usually a missing or mistyped Subscription Key: without a valid Ocp-Apim-Subscription-Key the API gateway rejects the request outright, with this exact message:

Access denied due to invalid subscription key. Make sure to provide a valid key for an active subscription.

Re-check the Subscription Key field in the connector settings, and confirm you are using the permanent key if your development subscription has lapsed. A development key that has passed its 90 days, or one that has used up its call quota, produces the same message — the subscription is no longer active either way.

Can one integration serve many end customers? Not under the maatwerkkoppeling flow this connector uses today. A productiekoppeling is the route for that, but it is a different authentication model, not a different form: SnelStart requires the OAuth authorization-code flow and a registered webhook URL for a productiekoppeling, while this connector authenticates with a custom grant_type=clientkey exchange. Serving many end customers therefore means building and certifying a second, OAuth-based integration alongside this one. Discuss that route with partner@snelstart.nl before committing to it.

Development key works, permanent key does not (or vice versa). Development and permanent subscriptions are distinct subscriptions on the Developer Portal. Confirm in the portal which subscription the key you pasted belongs to, and that it is still active.

For anything on the Apideck side of the setup, contact Apideck Support. For key issuance, certification status and the SnelStart account package, contact SnelStart at partner@snelstart.nl.