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5 steps to implement contact syncronization

1

Authorize access

Your user must first authorize your application to access their accounting platform (e.g., Xero, Lexware Office, Sevdesk) via an authorization flow (e.g., OAuth, API key) through maesn Connect.
2

Retrieve contacts

Fetch the relevant contacts from your user’s accounting platform using the GET /contacts endpoint.
3

Reconcile contacts

Match the contacts imported from your user’s accounting platform with any existing contacts in your application, using relevant fields like vatId, email and companyName. Update contacts with newer information from the accounting platform if available and resolve conflicting information.
4

Create contacts

Use the POST /contacts to create contacts that exist in your application, but not in your user’s accounting platform. Use PUT /contacts or PATCH /contacts to update contacts in your user’s accounting platform if your application has more recent information on a contact.
5

Keep your data fresh

After fetching contact data initially, you should make sure to keep your user’s contact data up to date by regularly retrieving data through the GET endpoints. The lastModified query parameter can be utilized on all our GET endpoints to save you the hassle of creating deltas to detect change. See our guide to keeping data fresh for more information!
You can utilize Webhooks to make this process more efficient.
Last modified on January 23, 2026