The verdict in three sentences
A payroll and HRIS API integration costs between GBP 13,000 and 34,000 for a 1,900-employee group, depending on the number of tools and data flows. It removes monthly re-keying, saves the payroll team 3 days a month and cuts errors by 70% as a 2026 order of magnitude. The key to success is a single employee master record and consistency checks before every payroll close.
Manual re-keying, flat files or API: what each option costs
In many retail groups, the HRIS (time, absence, reviews), the payroll software and the scheduling tool live apart. Every month, an administrator exports, reworks in Excel and re-imports. Three approaches exist.
| Option | Upfront cost | Annual cost | Reliability | Lead time |
|---|---|---|---|---|
| Manual re-keying | GBP 0 | 3 days/month x 12 = 36 admin days (about GBP 7,700) | Low, 2 to 4% of lines wrong | Immediate |
| Scheduled CSV imports | GBP 4,300 to 10,000 | GBP 1,700 to 3,400 maintenance | Medium, frequent rejects if formats change | 4 to 6 weeks |
| API integration with middleware | GBP 13,000 to 34,000 | GBP 3,000 to 6,000 maintenance and hosting | High, automated checks | 2 to 4 months |
| Standard vendor connector | GBP 2,600 to 8,500 + subscription | GBP 3,400 to 10,000 | Variable, limited to predefined fields | 1 to 2 months |
| Replace with a single suite | GBP 51,000 to 128,000 | Licenses GBP 7 to 13 per employee per month | High | 9 to 18 months |
For 1,900 employees, a single suite means GBP 160,000 to 296,000 in licenses per year. A custom integration keeps existing tools and costs about ten times less.
Flows to sync and what they cost
A serious integration does more than copy data. It must handle UK payroll specifics: mid-month starters, part-time hours, variable bonuses, statutory sick pay and RTI submissions to HMRC.
| Flow | Direction | Frequency | Indicative cost |
|---|---|---|---|
| Joiners and leavers | HRIS to payroll | Real time | GBP 2,600 to 5,100 |
| Contract, role and salary changes | HRIS to payroll | Daily | GBP 2,100 to 4,300 |
| Absence and leave | HRIS to payroll | Daily | GBP 2,100 to 5,100 |
| Overtime and premiums | Scheduling to payroll | Weekly | GBP 1,700 to 4,300 |
| Bonuses and sales commissions | Business tool to payroll | Monthly | GBP 1,700 to 5,100 |
| Payslip and cost data back | Payroll to HRIS | Monthly | GBP 1,300 to 3,400 |
| Consistency checks and exceptions report | Cross-system | Before close | GBP 1,300 to 6,800 |
Consistency checks make the difference: an employee in payroll but missing from the HRIS, an absence without a reason, a variable outside its usual range. The administrator works through an exceptions list instead of checking 1,900 lines.
Four-step method
- Flow mapping (2 to 3 weeks): inventory of fields, rules and employee identifiers in each tool.
- Middleware development (5 to 10 weeks): API connectors, message queue, automatic retry on error, log of every exchange.
- Parallel payroll (1 to 2 cycles): the old method and the integration run side by side and results are compared.
- Cutover and monitoring: failure alerts and a tracking dashboard for IT.
On compliance, payroll data is sensitive: encrypted exchanges, UK hosting, access limited to authorised staff and the audit trail required by UK GDPR.
Mini case study
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Thomas, CIO of a retail group in London (1,900 employees, 42 stores), finds that his three payroll administrators each spend 3 days a month re-keying data, 108 days a year. The loaded cost of an administrator day is GBP 215, so GBP 23,200 a year. On top come error corrections: 35 corrected payslips a month on average, at 30 minutes each.
He approves an integration at GBP 27,500 plus GBP 4,300 a year in maintenance. Estimated annual gain: GBP 23,200 of re-keying avoided and 70% fewer corrections, about 150 hours. The project pays back in roughly 15 months, and payroll close moves from D+5 to D+2.
FAQ
How much does a payroll and HRIS API integration cost in London in 2026?
Between GBP 13,000 and 34,000 depending on the number of flows and tools. An integration limited to joiners, leavers and absences starts around GBP 13,000.
Do our tools need an API?
It is preferable, and most payroll and HRIS vendors offer one in 2026. Otherwise, the integration can rely on secure file drops, at a 10 to 20% premium.
How long does the project take?
Plan 2 to 4 months, including 1 to 2 parallel payroll cycles to validate results. Cutover happens at the start of a month to limit risk.
What happens if a flow fails?
The middleware queues the message, retries automatically and alerts IT after 3 failures. No data is lost and every exchange is logged.
Is the integration compatible with RTI submissions?
Yes, it feeds the payroll software, which remains responsible for RTI filings to HMRC. Cleaner upstream data reduces the errors flagged on each Full Payment Submission.
Let's scope your project. Tell us your payroll, HRIS and scheduling tools and your headcount, and we will price an integration with a 2 to 4 month timeline. 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.
