Automating salary processing for enterprise organizations.

I led the backend development for this multi-tenant payroll system. The challenge was building something that could handle complex financial calculations across different organizations, each with their own unique payroll rules, tax structures, and deduction policies.

I designed the entire backend architecture using Clean Architecture principles and CQRS patterns. This meant separating business logic from infrastructure concerns, making the system maintainable and testable. I built the payroll calculation engine from scratch, implemented tax computation algorithms, and created a flexible deduction system that integrates with our loan management module.

The system handles everything from salary computation to bank API integration for disbursements. I also implemented robust audit trails for every financial transaction—crucial for compliance and financial reconciliation.

Payroll isn't just about multiplying hours by rates. Every organization has different policies, different tax brackets, different allowances, different deductions. Some have performance bonuses, others have 13th-month pay. Some deduct loans automatically, others don't.

The challenge wasn't technical complexity alone—it was building something flexible enough to handle this diversity while maintaining accuracy and speed.

For HR teams: They needed something that "just works." No manual calculations, no Excel formulas breaking, no wondering if taxes were computed correctly.

For employees: They wanted clarity. See their payslip, understand every deduction, know when loans would be paid off.

The technical reality: We needed multi-tenant architecture, a rule engine for flexible calculations, accurate tax algorithms, bank API integration, and bulletproof audit trails. Oh, and it had to be fast—payroll runs can't take hours.

I built the system using Clean Architecture with CQRS (Command Query Responsibility Segregation). This separation meant write operations (payroll runs, deductions) were isolated from read operations (reports, payslips), making the system both fast and maintainable.

The payroll engine: I created a rule-based calculation engine. Each organization defines their own rules—allowances, deductions, tax rates—and the engine applies them automatically. This meant we could onboard new clients without code changes.

Tax computation: I implemented PAYE (Pay As You Earn) tax calculations with support for different tax brackets and zones. The algorithm handles progressive taxation automatically.

Loan integration: Seamless integration with the loan management module. When payroll runs, outstanding loans are automatically deducted and updated. No manual intervention needed.