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API integration: connect your systems without retyping

Your accounting, CRM, online store, HR system and AI assistant exchanging data on their own. With an API integration, an order, customer or invoice is entered once and then appears everywhere it is needed. We connect any system, even when there is no standard integration.

Pick your systemWhat is an API integration?
4.8 from 127 reviews
Kiwa ISO 9001 certification markKiwa ISO 27001 certification markISO 9001 & 27001
Your online store or CRMWhere the work comes in
  • Orders and deals goes to Your accounting
  • Customers and contacts goes back and forth with Your accounting
  • Invoices goes to Your accounting
  • Payment status comes from Your accounting
Your accountingWhere the numbers add up

Built for clients including Tata Steel, M&G Investments, Digistore24, Toppers in Concert, Bar-le-Duc and Loogman

  • Tata Steel
  • M&G Investments
  • Signal.Stream
  • Amsterdam Dance Event
  • Tyson 2.0
  • StukTV
  • Digistore24
  • Bar-le-Duc
  • Verkade
  • RUMAG
  • ADC
  • TOTO
  • Data Science Lab
  • Qualogy
  • Complex
  • Xplct
  • DGI
  • Jack's Casino
  • Kosso Nutrition
  • Crocodile
  • Tata Steel
  • M&G Investments
  • Signal.Stream
  • Amsterdam Dance Event
  • Tyson 2.0
  • StukTV
  • Digistore24
  • Bar-le-Duc
  • Verkade
  • RUMAG
  • ADC
  • TOTO
  • Data Science Lab
  • Qualogy
  • Complex
  • Xplct
  • DGI
  • Jack's Casino
  • Kosso Nutrition
  • Crocodile
Explainer

An API integration is a connection between two systems that exchange data automatically through their APIs. An API is a fixed entrance that a system offers to other software. So an order from your online store lands in your accounting by itself, and a new customer lands in your CRM. Nobody retypes anything.

The integration decides which data moves, when, and in which direction. An API does nothing on its own, however. The integration is the software that ties the APIs of two systems together.

It handles four things:

  • Which data: orders, customers, products or invoices, and which fields of those need to come along.
  • The translation: a VAT code or general ledger account has a different name in one package than in the other.
  • The timing: every night, every fifteen minutes or straight away with every change.
  • What happens when it fails: try again, send an alert and show what got stuck.

You can read more about the API itself, and what to look for when you choose software, in what is an API.

Your online storeWhere the order comes in
Order 10423 items€249.00 incl. VATPayment status: paid
Order goes to the integration
Payment status goes to your online store
The integrationHandles four things
  1. Which dataOrder, customer and order lines
  2. The translation21% VAT becomes VAT code standard
  3. The timingStraight away with every new order
  4. When it failsTry again and send an alert
Sales entry goes to your accounting
Payment goes to the integration
Your accountingWhere the numbers add up
Sales entry 1042Ledger 8000, revenueVAT code: standardPayment received
API integration between an online store and accounting: order out, payment status back
Types of integration

Roughly five, from manual work to fully automatic: export and import, a standard integration, a custom API integration, a webhook and an MCP server for AI. Choose the simplest one that does what your process needs. A standard integration is fine if it handles the same fields, direction and exceptions as you do.

What types of integrations are there?
TypeHow it worksWhen
Type: Export and importHow it worksSomeone downloads a file from one system and uploads it into the otherWhenLow volumes, data may be a day old
Type: Standard integrationHow it worksA ready-made integration from a software package's marketplaceWhenYour process is common and the integration carries all fields
Type: Custom API integrationHow it worksYour own software that connects two or more APIs, with your rulesWhenYour own rules, more than two systems or missing fields
Type: WebhookHow it worksA signal a system sends when something happens; often part of an API integrationWhenWhen you want to react straight away to a new order or customer
Type: MCP serverHow it worksAn integration that lets an AI assistant such as ChatGPT or Claude reach your systemsWhenWhen AI needs to look up data or prepare something

Export and import works fine for low volumes. But it stays manual work, and the data is only as fresh as the last export. Also, a webhook is not an alternative to an API integration. The webhook reports that something happened; then the integration fetches the details through the API and passes them on.

Systems

For each system you can read which data you exchange, how the connection works technically, what the standard integrations do and where things get stuck in practice. We have worked out 24 systems, in 9 groups. If your system is not listed, we connect it too.

Accounting and ERP5 systems, 27 combinations

CRM and sales3 systems, 18 combinations

Ecommerce and payments4 systems, 17 combinations

HR and payroll3 systems, 13 combinations

Projects and service2 systems, 7 combinations

Office and collaboration2 systems, 5 combinations

Data and reporting1 system, 2 combinations

Public registers2 systems, 2 combinations

AI assistants2 systems, 15 combinations

Is your system not listed? We also integrate systems that don't have a page here, and systems without a standard integration. Tell us which system it is.

Combinations

Accounting with CRM, accounting with an online store, and HR with payroll. For each combination we explain what goes back and forth, at what moment and what to watch out for.

Want to connect your own software to a package? Then read Exact Online integration with your own software or AFAS integration with your own software. Two popular flows also have their own articles: connecting Shopify to your accounting and connecting HubSpot to your accounting.

Standard or custom

When a standard integration does not do what your process needs. That is the case when you combine more than two systems or need your own translation rules, such as a cost centre per branch. It is also the case when the standard integration misses the fields that matter, or when no standard integration exists between your packages.

If a standard integration does what you need, use it. Do check whether all the fields you use come along, and what happens when there is an error. If a standard integration fits, we will tell you.

Start with the flow, not with the technology. Write down what has to go from A to B and what has to come back: orders out, invoice status back. Each direction is a separate flow, with its own errors. So start with one flow. An API integration that tries to run six flows at once will break six times in the first month, and you will not know why.

Lead time

That depends on the number of flows, the number of fields and the state of your data. Most of the time does not go into building. Instead, it goes into agreeing which data leads and into testing with real exceptions. One flow between two systems with a good API is ready sooner than three systems at once.

Think of exceptions such as credit notes, partial deliveries and changed customer details.

Costs

The price of an API integration depends on the number of flows, the number of fields, how often the data has to move, the state of your data and the requirements for monitoring and recovery. On top of the build, budget a yearly amount for maintenance, because suppliers change their APIs.

What drives the price per type is set out in what a system integration costs. Set those costs against what retyping costs you now; the calculation is in what manual work costs.

Not sure yet which integration saves the most time?

In the AI Opportunity Audit we map your processes and systems side by side, with what the work costs now and which integration or automation gains the most.

See the AI Opportunity Audit
Why integrate

Less retyping, fewer errors and one up-to-date picture. What nobody retypes, nobody can retype wrongly. And when something does go wrong, you notice, because the integration reports it.

Less retyping

An order, customer or invoice is entered once and then appears everywhere it's needed. Nobody copies it across by hand any more.

Fewer errors

What isn't retyped can't be retyped wrongly. And when something does go wrong, you notice, because the integration reports it.

One up-to-date picture

Sales sees whether a customer has paid, finance sees what has been sold, and nobody works from last week's export.

AI and integrations

Through the same APIs. An AI assistant or AI agent needs an integration to look up data or prepare something in your accounting or CRM. You can do that with your own API integration or with an MCP server. For each integration you set what the AI may read, what it may change and what goes past a person first.

That is often where most of the time savings are, too. An integration moves data; in between, AI can read a document, sort an email or prepare a booking proposal. For anything that touches money or customers, a person approves it before it goes through.

For each system we explain how that works, for example connect Exact Online to ChatGPT and connect AFAS to Claude through MCP. What an AI agent is, and what it does with those integrations, is in what is an AI agent. Which work you can automate with it is in automating business processes with AI. You will find a ready-made role, such as the AI Invoice Checker, among our AI employees.

How we build an integration

In four steps: agree what goes where, translate the fields and rules, test with real cases and go live with logging and monitoring. The first step is on paper before anyone writes a line of code. That way everyone knows in advance which system leads.

  1. What goes where

    Which data moves, in which direction, and which system wins when two values differ. That is written down before anything gets built.

  2. Fields and rules

    For every field, how it translates between the systems: statuses, VAT codes, general ledger accounts, item numbers. And what happens with a duplicate or a missing value.

  3. Testing with real cases

    In a sandbox or test administration, with the exceptions you actually run into: credit notes, partial deliveries, changed customer details.

  4. Live, with logging and monitoring

    Every sync is logged, and when something fails, someone gets an alert. If a vendor changes its API, we update the integration.

Also agree who owns the integration on your side. Systems get updates, fields change and tokens expire. Someone has to decide on the translation tables and get the call when a flow stops. Larger projects, where an integration is part of your own software, fall under custom software.

Within this topic

All articles
Data model showing the fields synced between two systems

Integrations7 min read

Exact Online integration with your own software

An Exact Online integration ends manual re-keying, but often breaks on duplicate data. How to set the source, the direction and recovery when things fail.

Read the article
An overview of the fields exchanged between AFAS and an application of your own

Integrations6 min read

AFAS integration with your own software

AFAS integration works through connectors that must be set up first. How to choose the source, write data back safely and keep control of errors.

Read the article
A conversation walking through the steps between sales and the accounts team

Integrations6 min read

HubSpot integration with your ERP and accounting

HubSpot integration with your ERP and accounting: connect sales and invoicing without duplicate customers, with one direction per field and error recovery.

Read the article
The Your Tech Club team at the office in Amsterdam
Amsterdam
Who you'll talk to

With the people who build the integration. Not an account manager, but someone who builds integrations themselves and who will also tell you when a standard integration is enough.

Joey van VlietJoey van VlietFounder
Yassine SeghrouchniYassine SeghrouchniFounder
  • Office on the Duivendrechtsekade in Amsterdam
  • ISO 9001 and ISO 27001, certified by Kiwa
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Frequently asked questions

What is an API integration?

An integration lets two systems exchange data through their APIs, so nobody has to retype it. For example, an order from your online store becomes a sales entry in your accounting by itself, or a won deal in your CRM automatically becomes a project or invoice.

Can every system be connected?

Yes. If a system has an API, we connect through that API. If it does not, we look at what is there: an export, a shared folder, a database or an email the system sends. In the first conversation you will hear which route it will be.

When is a standard integration enough?

When it does what you need: the same fields, the same direction, the same exceptions. You need a custom integration for your own rules, for more than two systems, or when the standard integration just misses that one piece of data.

What happens when a supplier changes its API?

Then the integration has to change with it. That is why we log every sync, someone gets an alert when there is an error, and we agree who maintains the integration. So you do not discover a change only when a week of orders is missing.

How secure is an integration?

An integration only gets the permissions it needs, keys are not stored in the code and every action is logged. When personal data is involved, a data processing agreement under the GDPR is part of it. We work to ISO 27001 and ISO 9001, certified by Kiwa.

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