We replaced a SaaS provider's patchwork of local payroll vendors and spreadsheets with one auditable platform that keeps each region's tax rules separate. It brought 40+ regions together and removed 92% of the manual work.
Industry: HR TechService: SaaS & SoftwareUpdated
Overview
The challenge
The client paid staff around the world through 14 local payroll vendors and hundreds of spreadsheets. Because the numbers never lined up, nobody could see total labour costs in real time, and the risk of regional tax filing errors was high.
Every new country meant another vendor, another contract and another set of spreadsheets. The problem grew each time the business did.
Inconsistent local tax calculations led to a $200k+ audit penalty in the previous financial year.
The HR team spent 60% of each month reconciling payroll by hand instead of working on hiring.
Opening a new region took 3 months of vendor negotiation and API mapping, which held back growth into new markets.
The solution
We built a plug-in adapter layer that keeps each country's tax logic apart from the core payroll ledger, so a change in one region does not touch the others.
Every salary change and tax adjustment is saved as an event. That gives the team an accurate timeline of each employee's pay that can be replayed at any time.
Each payroll run produces a cryptographically hashed audit trail that records which version of every regional policy was applied.
Before and after
Before
12-16 Weeks
Each country needed vendor vetting, legal contracts and a custom API integration.
After
3 Weeks
The team configures a new regional adapter from pre-built Coretus compliance templates.
Before
External and manual
Calculations lived inside vendor portals, so nobody could see the logic until an error turned up.
After
Internal and governed
One shared rule engine records a reason code for every local tax deduction.
Before
Monthly batches
Global cost reports ran 30 days behind because regional providers reported late.
After
Live updates
Global payroll accruals update as soon as a change is made in the HR system.
Key features
We used the saga pattern to manage payments that touch several regional databases. If one step fails, the earlier steps are reversed, so nobody is paid twice and no bank file goes missing.
Business impact
100% payment integrity
AI checks flag unusual regional tax variations and payroll outliers before a run is finalised, which stops overpayments before they happen.
Business impact
↑ 4.2% of margin saved
Results
4x Faster Market Entry
Adapters now deploy automatically, so the company can start paying staff in a new country in about three weeks.
Before: 90 DaysAfter: 21 Days
92% Time Savings
With spreadsheet reconciliation gone, the HR team has its time back for hiring and people work.
Before: HighAfter: Minimal
100% Compliance Verified
Shared controls removed the manual steps where filing mistakes used to creep in.
Before: FrequentAfter: Zero
Faster delivery
These ready-made components cut out repeated setup, so most of the build time went on regional tax logic.
Handled OIDC sign-in and scoped permissions, so each payroll user saw only the regions and records their role allowed.
Gave every new country a ready-made adapter shell, leaving the team to configure only that region's tax rules.
Watched the central payroll ledger across all regions, giving the team one place to spot problems.
Applied safety checks to foreign exchange when pay moved between regions and currencies.
Trust and control
Regional database sharding keeps each employee's data inside the territory the law requires.
Data residencyField-level encryption and OIDC-based scoped access give the platform SOC 2-ready controls for payroll data.
Secure accessThe distributed cloud design handles 50,000+ payslips generated at the same time without slowing down.
Peak loadUnder the project delivery model, Coretus handed over the full source code, workflows and documentation, and ran a knowledge handover with the internal engineering team.
100% ownedThe provider paid 15,000+ employees through 14 local vendors and hundreds of spreadsheets. It had no live view of labour costs, had paid a $200k+ audit penalty the year before, and its HR team spent 60% of each month reconciling numbers. Opening a new region took about three months.
Each country's tax logic runs in its own adapter service, apart from the core payroll ledger. Every salary change and tax adjustment is stored as an event, and each pay run produces a hashed audit trail of the regional policy versions used. Adding a region means configuring a new adapter from templates.
Market entry became 4x faster, with new regions going live in 21 days instead of 90. Manual payroll admin fell by 92%, and regional tax filing errors went from frequent to zero, with no regulatory penalties. The HR team now spends the time it saved on hiring and people work.
If local vendors and spreadsheets are slowing your payroll down, we can help you plan one auditable platform that keeps each region's tax rules separate.