Help Singapore SMEs automate compliance tasks: GST calculation, PEPPOL invoice validation, tax report generation, and regulatory checklist.

Quick Start

Check GST registration requirements:

# Check if business needs GST registration (threshold: S$1M annual turnover)
curl -s "https://www.iras.gov.sg/api/gst-threshold-check" -d '{"turnover": 1000000}'

GST calculation:

# Calculate GST (9% as of 2024)
curl -s "https://api.gstcalculator.sg/calculate" -d '{"amount": 1000, "rate": 0.09}'
# Returns: {amount: 1000, gst: 90, total: 1090}

Key Features

1. GST Registration Checker

Singapore businesses must register for GST if:

• Annual taxable turnover exceeds S$1 million (mandatory)
• You expect turnover to exceed S$1 million in next 12 months (voluntary)

Usage:

# Check registration requirement
echo "Check GST registration for turnover: S$1,200,000"

2. GST Calculator

Current GST rates:

• 2023: 8%
• 2024 onwards: 9%

Calculate GST:

# For invoice amount
Invoice: S$5,000
GST (9%): S$450
Total: S$5,450

3. PEPPOL Invoice Validator

Singapore uses PEPPOL (InvoiceNow) for e-invoicing.

Validate PEPPOL invoice:

• Check UEN format (9 or 10 characters)
• Verify invoice structure (UBL 2.1 format)
• Validate against IRAS requirements

Checklist:

• [ ] Supplier UEN present
• [ ] Buyer UEN present
• [ ] Invoice number unique
• [ ] Tax amount calculated correctly
• [ ] Currency code (SGD)
• [ ] Payment terms specified

4. Monthly GST Return (GST F5) Helper

Required data for GST F5:

• Box 1: Total value of standard-rated supplies
• Box 2: Total value of zero-rated supplies
• Box 3: Total value of supplies (Box 1 + Box 2)
• Box 4: Output tax due
• Box 5: Input tax claimed
• Box 6: Net GST payable/refundable

Monthly checklist:

□ Collect all tax invoices (purchases)
□ Collect all tax invoices (sales)
□ Calculate output tax (sales)
□ Calculate input tax (purchases)
□ Reconcile with accounting records
□ File GST F5 by deadline (1 month after period end)

5. Compliance Calendar

Key deadlines:

• Set up auto-reminders 7 days before deadline
• Prepare documents 3 days before filing
• Keep records for 5 years (IRAS requirement)

Common Compliance Scenarios

Scenario 1: New Business Registration

Steps:

• Register business with ACRA
• Get UEN (Unique Entity Number)
• Check if GST registration required
• Set up accounting system
• Register for CorpPass (for digital services)

Scenario 2: Importing Goods

Requirements:

• Customs import permit
• Pay import GST (7% or 9%)
• Claim input tax (if GST registered)
• Keep import documentation

Scenario 3: Exporting Goods

Requirements:

• Zero-rate exports (0% GST)
• Keep export documentation
• Declare in GST return (Box 2)

IRAS Resources

• GST Registration/gst-registration)
• GST F5 Filing/filing-and-payment)
• PEPPOL/InvoiceNow
• CorpPass

Penalty Information

Late GST Filing:

• First offence: S$200 penalty
• Repeat offence: S$500-S$5,000
• Continued failure: Prosecution possible

Incorrect Information:

• Up to 200% of tax undercharged
• Criminal prosecution for fraud

Automation Workflows

Monthly GST Preparation (Automated)

Day 1 of new month:

• Fetch all sales invoices from previous month
• Calculate total output tax
• Fetch all purchase invoices
• Calculate total input tax
• Generate GST F5 draft
• Send reminder to accountant

Commands:

# Generate monthly GST summary
echo "Generate GST report for $(date -d 'last month' '+%Y-%m')"
# Calculate totals
Output Tax: Sum of GST on all sales invoices
Input Tax: Sum of GST on all purchase invoices
Net GST: Output - Input

Quarterly Compliance Check

End of each quarter:

• Review all transactions
• Verify GST calculations
• Check PEPPOL compliance
• Update compliance calendar
• Prepare for GST F5 filing

Integration Examples

With Accounting Software

Xero/QuickBooks integration:

# Export sales data
curl -s "https://api.xero.com/api/Invoices?status=PAID" \
  -H "Authorization: Bearer TOKEN"
# Export purchase data
curl -s "https://api.xero.com/api/Bills?status=PAID" \
  -H "Authorization: Bearer TOKEN"

With IRAS MyTax Portal

File GST F5 via API:

# Submit GST return (requires CorpPass authentication)
curl -s "https://apiservices.iras.gov.sg/gst/f5" \
  -X POST \
  -H "Authorization: Bearer CORPPASS_TOKEN" \
  -d '{"period": "202403", "box1": 100000, "box4": 9000, ...}'

Error Handling

Common Errors

"GST registration required"

• Turnover exceeded S$1M
• Action: Register within 30 days

"PEPPOL invoice rejected"

• Invalid UEN format
• Missing required fields
• Action: Validate against InvoiceNow schema

"Late filing penalty"

• File immediately
• Pay penalty
• Set up auto-reminders

Best Practices

• Keep digital records - IRAS accepts digital records
• Reconcile monthly - Don't wait until quarter end
• Use accounting software - Xero, QuickBooks, SQL Accounting
• Set up auto-reminders - Never miss a deadline
• Review input tax claims - Ensure all claims are valid
• Keep export documentation - For zero-rated supplies
• Train staff - On GST requirements and PEPPOL

Support Resources

• IRAS Helpline: +65 1800 356 8300
• InvoiceNow (PEPPOL): +65 6248 0909
• ACRA: +65 6248 6000
• Enterprise Singapore: +65 6898 1800

Updates

• 2026-03-27: Initial release
• GST rate: 9% (2024 onwards)
• PEPPOL mandatory for government suppliers
• B2B PEPPOL expansion expected 2027-2028