Connecting your software to bexio or Abacus: what an integration involves

bexio and Abacus are business software from two Swiss companies: bexio AG in Rapperswil and Abacus Research AG in Wittenbach. Both publish interfaces that other software can use to read and write their data. This article is based on their public developer documentation as it stood on 20 October 2026. Interfaces change, so check the current version before you plan.

What can be connected?

Customers, documents, bookings and more, according to the vendors' own documentation. bexio's interface covers contacts, quotes, orders, invoices, supplier bills, accounting, bank payments, items, projects, timesheets, files and payroll. Abacus offers interfaces across its applications, from addresses and accounting to payroll, projects and electronic banking, as far as your installation and licences include them.

For example:

• a job marked as finished in your software becomes an invoice in the accounting;
• a new customer entered in one system appears in the other;
• open invoices from the accounting show up in your software, so staff can see what a customer owes;
• hours recorded in your software are booked to the right project.

Check the details you need, not just the headings. bexio's own FAQ says "we are not able to support every use case via API yet", and on 20 October 2026 it listed credit notes as not available. Abacus notes on its API Hub that parts of its documentation are generated from versions not yet released, and advises: "To be sure that an interface is available on a particular Abacus Version please check the Abacus APIs on the installation itself."

What do the bexio and Abacus interfaces offer?

bexio offers an online interface, a REST API that exchanges data in JSON, which your software uses with the consent of a bexio user. Abacus lists three kinds on its API Hub: REST APIs based on the OData 4.0 standard, the AbaConnect interfaces for importing and exporting data, and ODBC and JDBC access. Which of them you can use depends on your Abacus installation and licences.

bexio

• REST and JSON: bexio's API uses "HTTPS methods and RESTful endpoints to create, edit, and manage documents in the bexio system", with JSON "as the data interchange format".
• Access with consent: your software is registered as an app in bexio's developer portal, and a bexio user agrees to the access it asks for. bexio asks apps to "only request the scopes that you need", and the connection works "with the user rights of the user who set up the connection".
• No shared personal tokens: a personal access token "has full access to your company's data", is valid for 60 days and is "strictly intended for personal use". When another party needs access, bexio says "you must use the Authorization Code Flow instead", the consent route above.
• A rate limit: bexio limits "the number of requests a company can make per minute" and answers with an error (code 429) once the limit is reached.
• Changes: bexio says it lists "any changes to the current version of the API" with their dates; the newest entry on 20 October 2026 was from 19 June 2026.
• Support: bexio provides the API "as is", with "no guided implementation or code support available".

Abacus

• REST with OData 4.0: Abacus describes its API as "an Interface for processing and returning REST Request/Response Pairs as per OData 4.0 Specification".
• A service user: access runs through a service user set up in Abacus, which "can only access Abacus via the available interfaces (access to the Abacus UI is not possible)". Its secret is shown once, when it is created, and never again.
• Licences: for a connection built for one company, Abacus describes an "Individual" licence, "used for custom solutions built for specific customers". The Abacus application must be installed with its AbaConnect option enabled, the service user "counts towards one user of application access", and each Abacus client used with the API has to be enabled, which Abacus says has "pricing implications".
• Rate limits: as of Abacus 2026, client programs should stay within 400 requests per minute, 18,000 per hour and 40,000 per day (200, 12,000 and 30,000 up to version 2025).
• Changes over time: subscriptions "are used to track changes in the Abacus system", so your software can fetch what has changed instead of reading everything again. Each API version "is supported for at least 3 years".
• AbaConnect: Abacus calls it "a central Abacus Framework for importing and exporting data to and from Abacus Applications", by XML file and, for many interfaces, as a web service. The framework needs no separate licence, but "depending on the specific AbaConnect interface, a licence option may be required".

What does an integration need from you?

Access, and a few decisions. For bexio: a user with the right permissions who agrees to the connection. For Abacus: a service user, the right licence options and the API enabled for your client. For both: which data flows in which direction, which system leads for each kind of record, and what happens when the two disagree.

Access. In bexio, the connection reaches only what its user may see: "a user which doesn't have access to the contact will not have access to the contact via an API connection". So the choice of that user matters. For Abacus, the detailed licensing information is "only available to Abacus sales partners", so the partner who supports your Abacus installation is the one to ask about licences and enabling the API.

Decisions.

• Direction: one way (your software sends invoices to the accounting) or both ways (customers kept the same in both systems).
• Which system leads: for each kind of record, one system has the final say. Customers might live in your software, invoices and payments in the accounting.
• Timing: on every change, or collected and sent at set times. Both vendors limit the number of requests, which matters when volumes are large.
• Mapping: which field goes where, such as VAT codes, accounts, cost centres and payment terms.
• Errors: who is told when a record is rejected, and how it is put right.

How is an integration checked?

On test data first, never on your live books. bexio offers sandbox accounts for development, and Abacus runs a test server with demo data for each version. Automated tests then cover the normal cases and the awkward ones: a rejected record, a rate limit reached, a record changed in both systems at once, and a connection that drops halfway.

• bexio: for development work, bexio asks for "a bexio API sandbox account". Deleting is final there ("delete actions permanently delete resources. It cannot be undone."), so tests that delete never run against real data.
• Abacus: "A test server is available for each version of Abacus and can be used for API testing." The servers run builds not yet released, their data is erased after at most 45 days, and "under no circumstances may customer data or private data be saved on the server".
• Before launch: in the software we build, the whole connection first runs in a test version, we test it there right through from start to finish, and it goes live only when everything works.
• After launch: the jobs that move data between systems run in the background, where a failure is easy to miss. Monitoring is a service you book with us: every hour we check the software, scheduled tasks included, each part on its own, and a failed check sends the alarm to us. With monitoring, your software also gets its own status page, like ours.
• When the interfaces change: bexio lists the changes to its API with their dates, and Abacus supports each API version for at least three years, with at least a year as "deprecated" before it is switched off. Someone has to watch for both.

Build it in, or buy a connector?

Buy a ready-made connector if it moves exactly the data you need, in the direction you need, and tells you when something fails; bexio lists ready-made integrations in its Marketplace. Build the connection into your software when it is part of your own process, follows your own rules or links data no connector covers. Either way, someone has to keep it working when an interface changes.

bexio's own API page points users "looking for a ready-made integration (e.g., archiving, time tracking)" to its Marketplace, and developers who want "a bespoke integration with bexio for your business or your software" to the API. Questions to ask of any connector:

• Does it carry the fields you need, such as VAT codes and cost centres?
• Does it work in both directions, if you need that?
• Who is told when a record fails, and how?
• Who updates it when bexio or Abacus changes its interface?
• What does it cost per month, compared with building the connection once?

When the connection is part of software built for you, it is one more feature, specified, built and tested with the rest. The choice is close to the one between a standard tool and custom software: see custom software or an off-the-shelf tool. For what to automate in the back office in the first place, see back-office automation.