Double-Entry Finance Engine

Overview

The Finance Engine is a Go service that handles all accounting operations using double-entry bookkeeping.

Why Go?

Requirement	Go Advantage
Transaction Safety	Strong error handling
Concurrency	Goroutines for parallel processing
Decimal Precision	shopspring/decimal library
Performance	Low latency for financial ops

Core Concepts

Every Transaction Balances

Total Debits = Total Credits

Account Types

Type	Debit	Credit
ASSET	Increase	Decrease
LIABILITY	Decrease	Increase
EQUITY	Decrease	Increase
REVENUE	Decrease	Increase
EXPENSE	Increase	Decrease

Transaction Examples

Invoice Generated

Debit:  Student Receivable (1310)  Rs. 25,000
Credit: Tuition Income (4100)      Rs. 20,000
Credit: Transport Income (4200)    Rs.  5,000

Payment Received

Debit:  Bank Account (1200)        Rs. 25,000
Credit: Student Receivable (1310)  Rs. 25,000

Refund Issued

Debit:  Student Receivable (1310)  Rs.  5,000
Credit: Bank Account (1200)        Rs.  5,000

Implementation

type FinanceEngine struct {
    db *pgxpool.Pool
}

func (e *FinanceEngine) CreateTransaction(entries []LedgerEntry) error {
    // 1. Validate balance
    // 2. Begin DB transaction
    // 3. Insert transaction header
    // 4. Insert ledger entries with running balance
    // 5. Commit or rollback
}

Reports

Trial Balance

SELECT 
    a.code, a.name, a.type,
    SUM(le.debit) as total_debit,
    SUM(le.credit) as total_credit
FROM accounts a
JOIN ledger_entries le ON le.account_id = a.id
GROUP BY a.id

Account Ledger

SELECT 
    t.transaction_date,
    t.description,
    le.debit,
    le.credit,
    le.balance_after
FROM ledger_entries le
JOIN transactions t ON t.id = le.transaction_id
WHERE le.account_id = $1
ORDER BY t.transaction_date