Custom Asperion integration development
Appfront builds custom Asperion integrations that automate your accounting, invoicing and administration, from your webshop, CRM, PSP or in-house application. Through the Asperion REST API and OAuth 2.0, we synchronise sales invoices, general ledger accounts, VAT codes and contacts without manual re-keying. You save administrative time and keep your figures up to date at all times.
What is an Asperion integration?
Asperion is Dutch online accounting and invoicing software for freelancers, SMEs and accountancy and bookkeeping firms. Alongside bookkeeping, invoicing, VAT returns, bank feeds and scan & recognise, Asperion offers an open REST API, so other systems can communicate directly with the administration.
In practice, a custom integration means programmatically creating sales invoices and debtors from your webshop or CRM, processing payments from a PSP, synchronising contacts and articles, and reading general ledger and VAT data for reporting. This removes the manual re-keying between your systems and your accounts, and keeps your figures accurate in real time.
Appfront builds to the official Asperion REST API documentation and the OWASP ASVS security standard. We test first against the Asperion sandbox environment and its Swagger documentation, then align booking logic, mapping and error handling with your actual administrative processes, so the integration remains reliable even at peak volumes.
Book invoices automatically
Sales invoices and debtors are created directly in Asperion via the API, from your webshop, CRM or point of sale. No more manual re-keying: orders and payments flow neatly and consistently into your accounts.
Ledger in balance
Journal entries and ledger movements flow to Asperion via the API, or are read out for reporting. Your trial balance and profit and loss stay current, without anyone having to post entries by hand.
VAT without the arithmetic
The correct VAT codes are sent with each transaction, so rates are applied consistently. Your VAT return in Asperion is based on accurate, traceable figures rather than manual corrections.
Our development process for Asperion integrations
We work to a proven methodology that removes uncertainty early and delivers a stable integration. From an initial analysis of your administrative processes, data flows and source systems through to go-live and ongoing management, every step is aimed at an integration your team can understand and trust.
We map out which data must flow between your systems and Asperion: sales invoices, contacts, ledger or VAT, in which direction and with what booking logic.
We design the integration architecture, configure OAuth 2.0 against the Asperion sandbox, and define a mapping and error-handling strategy.
Implementation with automated tests, structured logging and monitoring. You see working builds along the way.
Controlled go-live with data validation and a safety net, followed by ongoing management and further development.
What an Asperion integration delivers in practice
Every Asperion integration is tailored to your type of administration, data flows and adjacent systems. Below are the features we most often deliver for organisations that use Asperion as their financial foundation.
Asperion REST API & OAuth
We connect via the official Asperion REST API using OAuth 2.0 (authorisation code flow), tested first against the sandbox environment and Swagger documentation. Tokens are managed securely and refreshed automatically, so the integration keeps running reliably.
Sales invoice synchronisation
Orders from your webshop, CRM or point-of-sale system are booked into Asperion as sales invoices via the salesinvoices endpoints, including invoice lines and debtor. You can also create invoices as drafts for review before they are finally booked.
General ledger & journal entries
Journal entries are created via the API, or general ledger movements are read out for reporting and dashboards. We carefully configure the mapping to your chart of accounts, so that bookings consistently land on the correct general ledger account.
VAT & tax return data
For each transaction we pass on the correct VAT code, retrieved from the vatcodes endpoint. This ensures rates are applied consistently and that the basis for your VAT return in Asperion is traceable and correct, even at high transaction volumes.
Relations & Debtors
Debtors and creditors are synchronised two ways with your CRM or webshop via the debtors and creditors endpoints. Address, contact and payment details stay the same in both systems, so invoicing and collections run smoothly.
Webshop & PSP integration
Orders from your webshop and settlements from a PSP are automatically processed into invoices and payments in your accounts. One continuous flow from order to booking, with clear reconciliation against your general ledger.
Typical use cases in practice
An Asperion integration looks quite different from one organisation to the next. We see a number of recurring patterns, and for each we have a proven setup with attention to mapping, booking logic and the correct VAT and contact data.
Small and medium-sized business
Businesses that want to connect their sales, purchasing and time-tracking flows with their accounting. Sales invoices, relations and ledger movements flow automatically into Asperion, so the books are accurate in real time. See also our API integrations.
Webshop & e-commerce
Webshops that want orders and payments automatically booked as sales invoices in Asperion. PSP settlements, VAT rates and debtors are handled neatly, so your accounting grows along with your order flow. Read more about our e-commerce development.
Accountancy & bookkeeping firms
Firms managing multiple administrations who want to eliminate repetitive work. We bundle integrations for sales invoices, contacts and the general ledger per administration, so your team re-keys less and has more time to advise clients.
Freelancers & service providers
Self-employed professionals who manage quotes, invoices and hours in their own tool or CRM and want to pass that data on to their accounts. Sales invoices and relations land in Asperion automatically, so you spend less time on administration.
Technology we use
We build Asperion integrations using the official REST API and OAuth 2.0, combined with the backend stack that suits you. The exact choice depends on your source systems and data flows, so that your own team can manage or further develop the integration.
Why choose Appfront for your Asperion integration?
Appfront has extensive experience building API integrations for a wide range of organisations in the Netherlands. We always start with a thorough analysis of your existing systems and processes. An integration should not only work technically, but also add practical value to your administration.
For every integration, we write clear documentation and make sure your own team, or any future supplier, can understand and manage it. No black box, just transparent code and clear agreements on monitoring, alerting and maintenance.
You work with a dedicated point of contact who understands both the technical and the functional side. This keeps communication short, prevents misunderstandings and speeds up decisions when choices need to be made during development.
Also explore our wider services around API integrations, middleware, custom software and web app development. Prefer to work with a different accounting package? Then take a look at our Reeleezee integration.
- Experience with the Asperion REST API, OAuth 2.0 and the sandbox environment
- Specialists in integrations between webshops, CRM, PSPs and accounting
- Familiar with sales invoices, general ledger, VAT codes and relation synchronisation
- Secure by default — token rotation, secure vaults, scoped permissions
- Structured error handling and retry mechanisms
- Comprehensive logging and monitoring from day one
- Clear documentation your team can read and manage
- A fixed point of contact, no account managers passed around
- Ongoing maintenance and proactive further development
- A way of working aligned with your existing IT landscape
Security and privacy in Asperion integrations
An accounting integration always involves financial and personal data, such as invoices, debtors, bank details and VAT data. Appfront builds to the OWASP ASVS and uses Asperion's OAuth 2.0 authorisation, so we never work with passwords but with scoped, revocable tokens. We store tokens and client secrets in secure vaults, apply least-privilege permissions and keep authorisation separate for each integration. Read more about our OWASP ASVS approach.
Because this concerns financial administration, we carefully document the booking logic and data flows and build in controls against duplicate or incorrect postings. We record which data is exchanged so that your record of processing activities is complete and you can demonstrably comply with the GDPR. Access to production data is strictly separated and traceable through audit logs.
More on our security approach: information security policy and CVD policy.
- GDPR-compliant data processing and data minimisation
- OAuth 2.0 with scoped, revocable tokens
- Encryption in transit (TLS 1.2+) and at rest
- Role-based access and least-privilege principles
- Audit logs with traceable data flows
- Controls against duplicate or incorrect postings
- Automatic retries and dead-letter queues
- Documentation for your record of processing activities
Frequently asked questions about Asperion integrations
Answers to the questions we are asked most often about Asperion integrations.
An Asperion integration is a technical link between Asperion and another system, such as your webshop, CRM, PSP, till system or in-house application. Through the Asperion REST API, objects such as sales invoices, debtors, general ledger accounts and journal entries can be created and retrieved programmatically. This means orders, payments and customer records flow into your accounts automatically, without manual re-entry. An integration can be simple (booking webshop orders as sales invoices) or comprehensive (full two-way synchronisation of customers, products and the general ledger).
Asperion suits freelancers, SMEs, and accountancy and bookkeeping firms that keep their books and invoice online and need an open REST API for integrations. It is a strong choice if you manage multiple administrations or want to connect your webshop, stock or time registration to your accounts. Whether Asperion is the best fit for your situation depends on your choice of package and the systems you want to connect, which we will assess together during the analysis.
A simple integration, such as webshop orders being booked as sales invoices in Asperion, is usually quicker to deliver than a full two-way synchronisation of customers, products, the general ledger and VAT codes. The timeline depends on the number of data flows, the required synchronisation frequency and the complexity of the booking logic. After an intake meeting, we will give you a realistic estimate.
We work with the official Asperion REST API and OAuth 2.0 (authorisation code flow), combined with the backend stack that suits you: Node.js, Python, PHP, .NET, Ruby or Go. We build and test first against the Asperion sandbox environment with its accompanying Swagger documentation, and use endpoints for sales invoices, debtors, general ledger accounts, journal entries, VAT codes and items, among others, before going live.
The cost is determined by the complexity of the data flows, the number of systems to connect, the required synchronisation frequency and the amount of custom work in the booking logic. Ongoing management, monitoring and support also affect the total investment. We always provide a clear quote after a no-obligation analysis of your situation.
Yes. The Asperion API works with OAuth 2.0, so we never work with passwords but with scoped, revocable tokens. Appfront builds to the OWASP ASVS: tokens and client secrets are kept in secure vaults, with least-privilege authorisation and separate permissions for each integration. Because an accounting integration touches financial and personal data, we document the data flows so that your record of processing activities remains complete and you can demonstrably comply with the GDPR.
Yes. Appfront regularly takes over existing integrations, even if they were originally set up by another party. We review the API integration, the OAuth configuration, the booking logic and the error handling, document the current setup and propose improvements. From that point on, we can take care of adjustments, extensions and monitoring, including timely rotation of tokens and secrets.
Asperion suits freelancers, SMEs, webshops and accountancy and bookkeeping firms that want to handle their bookkeeping and invoicing online. Typical integrations include automatically booking webshop or till orders as sales invoices, processing PSP settlements, synchronising customers and debtors with a CRM, and making ledger and VAT data available for reporting. For firms managing multiple administrations, we bring these flows together in a single, manageable integration.
Ready to build your Asperion integration?
Tell us which systems you want to integrate with Asperion and which data (sales invoices, customers, ledger or VAT) needs to be synchronised. We are happy to help with mapping, booking logic and OAuth setup. A no-obligation first conversation will give you a clear picture of the possibilities within half an hour.