GST & AUD Currency Update - March 17, 2026

Summary

Successfully migrated all invoices from USD to AUD currency and implemented automatic 10% GST (Goods and Services Tax) calculations for Australian compliance.

Database Changes

New Columns Added to invoices table:

• tax_rate - NUMERIC(5,2) DEFAULT 10.00 - Tax rate as percentage
• tax_amount - NUMERIC(10,2) DEFAULT 0 - Calculated tax amount in currency

Schema Updates:

• Changed default currency from 'USD' to 'AUD'
• Added index on currency column for performance

Migration Results

Invoices Updated:

• 502 invoices converted from USD/usd to AUD
• 502 invoices had GST calculated retroactively
• 108 invoices had totals corrected to include GST

GST Calculation:

• Default rate: 10% (Australian GST)
• Formula: tax_amount = subtotal × (tax_rate / 100)
• Total: total = subtotal + tax_amount

Code Changes

Backend (rmm-psa-backend):

1. routes/invoices.js:
   • Changed default currency from 'USD' to 'AUD'
   • Auto-calculate GST on invoice creation
   • Auto-calculate GST on invoice updates
   • Include tax_rate, tax_amount, subtotal in INSERT/UPDATE queries
2. routes/invoice-payments.js:
   • Changed Stripe payment intent currency from 'usd' to 'aud' (lowercase)
   • Payment amounts now in AUD cents
3. migrations/2026_03_17_add_gst_to_invoices.sql:
   • Database migration script for GST columns
   • Currency conversion SQL
   • Retroactive tax calculations

Frontend (rmm-psa-dashboard):

1. src/pages/InvoiceDetail.jsx:
   • Display dynamic tax rate (reads from invoice.tax_rate)
   • Use tax_amount field from backend (with fallback to tax_total)
   • Show GST breakdown in totals section

Invoice Display Format

Before:

Total: USD $500.00

After:

Subtotal (ex GST): AUD $500.00
GST (10%):         AUD $50.00
─────────────────────────────
TOTAL (inc GST):   AUD $550.00

Stripe Integration

• Payment intents now created in AUD currency
• Stripe automatically handles AUD payment processing
• Connected accounts must support AUD (verify with Stripe)

Testing Results

Sample invoices verified:

• ✅ Invoice #20: AUD $191.64 + GST $19.16 = $210.80
• ✅ Invoice #503: AUD $500.00 + GST $50.00 = $550.00
• ✅ Invoice #504: AUD $150.00 + GST $15.00 = $165.00
• ✅ Invoice #505: AUD $75.00 + GST $7.50 = $82.50

All calculations verified correct within 1 cent tolerance.

Deployment Status

• ✅ Backend: Deployed (commit c4c5640)
• ✅ Frontend: Deployed (commit 1551770)
• ✅ Database: Migrated (502 invoices)
• ✅ Stripe: Configured for AUD

Future Considerations

1. Multi-Currency Support: If needed, the tax_rate column allows per-invoice tax rates
2. Tax Exemptions: Can set tax_rate=0 for tax-exempt invoices
3. Different Tax Rates: System supports variable tax rates per invoice
4. Currency Symbol: Frontend displays currency code (AUD) - could add $ symbol for AUD

Rollback Instructions

If rollback is needed:

-- Restore USD currency
UPDATE invoices SET currency = 'USD';
ALTER TABLE invoices ALTER COLUMN currency SET DEFAULT 'USD';
 
-- Remove GST (set to 0)
UPDATE invoices SET tax_rate = 0, tax_amount = 0;
UPDATE invoices SET total = subtotal;

Note: Stripe payments already processed in AUD cannot be automatically converted back.

Support Notes

• GST is automatically calculated for all new invoices
• Existing invoices have been retroactively updated
• Invoice totals include GST (clearly labeled)
• Customers will see AUD pricing on all invoices and payment pages
• Test card payments (4242...) work with AUD in Stripe test mode

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Generated: March 17, 2026 Migration completed successfully ✅