The verdict in three sentences
For a 600-employee group in Amsterdam, a connector between a custom HR app and a payroll system such as Nmbrs or AFAS costs 15,000 to 35,000 EUR in 2026 (market estimate) and is delivered in 6 to 10 weeks. It ends the rekeying of absences, bonuses and overtime by exporting the payroll variables every month, preceded by consistency checks before close. The expected gain is 2 to 3 days of payroll close per month and a clear drop in corrected payslips.
Options to feed payroll without rekeying
The HR director sees payroll administrators copying data every month that was already entered elsewhere: absence requests approved in the HR app, bonuses decided by managers in a spreadsheet, overtime from the time clock. Here are the possible approaches in 2026, with Toulouse figures for reference.
| Option | Upfront cost (2026 estimate) | Recurring cost | Pre-close checks | Timeline | Main limitation |
|---|---|---|---|---|---|
| Manual rekeying (current state) | 0 | 50 to 70 administrator hours a month | Visual, case by case | None | Errors and late close |
| Spreadsheet import into payroll | 2,000 to 6,000 EUR | Manual file preparation | Weak | 1 to 2 weeks | The spreadsheet remains an error source |
| Custom connector, HR app to Nmbrs or AFAS (Amsterdam) | 15,000 to 35,000 EUR | Maintenance 200 to 500 EUR a month | Yes, configurable rules | 6 to 10 weeks | Depends on HR data quality |
| Same connector to Silae in Toulouse (for reference) | 10,000 to 25,000 EUR excl. VAT | 150 to 400 EUR a month | Yes | 6 to 10 weeks | Same |
| Off-the-shelf HRIS with standard connector | 6,000 to 18,000 EUR deployment | 6 to 15 EUR per employee per month | Partial | 8 to 16 weeks | 600 employees = 3,600 to 9,000 EUR a month |
| Kolonell HR app with connector (medium complexity) | 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) | maintenance 75,000 FCFA a month | Yes | 6 to 10 weeks | Remote team, video workshops |
Amounts are market estimates. Both Nmbrs and AFAS expose APIs for payroll mutations; the exact exchange method depends on your licence and payroll provider.
The consistency checks that shorten the close
A connector is only worth its checks. Exporting wrong data faster helps no one. Here are the most cost-effective rules to configure.
| Check | Example anomaly detected | Observed frequency (order of magnitude) | Effect |
|---|---|---|---|
| Absence without manager approval | Leave entered but not approved | 2 to 5 % of absences | Blocked before export |
| Overlapping absences | Sick leave and holiday on the same day | 0.5 to 1 % | Administrator alert |
| Overtime above the cap | More than 48 hours in a week | 1 to 3 % of employees affected | HR and manager alert |
| Bonus without reference | Bonus entered with no reason or pay code | 3 to 8 % of bonuses | Sent back to the manager |
| Leaver with variables | Bonus for an employee who left last month | Rare but costly | Blocked |
| Variance against prior month | Variable more than 50 % above average | 1 to 2 % | Targeted visual check |
A typical project runs as follows: 1 to 2 weeks mapping pay codes with the payroll team, 3 to 5 weeks building the connector and checks, then 2 payroll cycles in parallel where the old and new flows coexist. This parallel run is essential: no payroll should switch over without comparing two months of results.
Legally, payroll variables are personal data under GDPR, and some absences reveal health information, which Dutch law treats strictly. Role-based access, change logging, EU hosting and, where applicable, consultation of the works council (ondernemingsraad) belong in the specification.
Mini case study
Eva, HR director of a 600-employee services group in Amsterdam, has 3 payroll administrators. Each month they spend 60 hours rekeying and checking variables, and about 9 payslips need correcting afterwards, at one hour per correction.
- Rekeying cost: 60 h x 50 EUR loaded cost = 3,000 EUR a month.
- Correction cost: 9 h x 50 EUR = 450 EUR a month.
- Connector at 25,000 EUR plus 300 EUR a month of maintenance: net gain of about 3,150 EUR a month.
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The project pays back in about 8 months, and close moves from the 27th to the 24th or 25th of the month, leaving 2 to 3 days to review payslips. This scenario is illustrative, to be recalculated with your real volumes.
FAQ
Do Nmbrs and AFAS accept automated variable imports?
Yes, both offer APIs and import formats for payroll mutations. The connector follows the method your licence or payroll provider supports, which can move the budget by 10 to 20 %.
Do we need to change payroll software?
No, the goal is precisely to keep your payroll system and feed its variables cleanly. Switching payroll software usually means a 3 to 6 month project and much higher risk.
How many days of close can we save?
Companies with 300 to 1,000 employees generally save 2 to 3 days a month. The gain depends on the number of variable sources and how disciplined managers are with approvals.
What happens if there is an error after export?
Every export is timestamped and replayable, and checks block known anomalies before sending. A correction is made in the HR app, then a new partial export is generated within minutes.
Can the connector handle several group entities?
Yes, provided it is planned during mapping: each entity has its own pay codes and collective agreements (CAO). Add 15 to 25 % to the budget beyond 3 entities.
Our custom web applications page presents our method, and our cybersecurity offer covers protection of sensitive data.
Let's scope your project. Send us your variable sources, headcount, number of entities and payroll system: we will price the connector, the checks and the parallel-run plan through a free quote. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
