1. Purchase Order Reference: Include when the invoice relates to a specific purchase order or contract number

2. Project Details: Add for project-specific billing with milestone or phase information

3. Discount Terms: Include when early payment or volume discounts are offered

4. Currency Information: Add for international transactions or when dealing with multiple currencies

5. Contact Information: Include specific department or person responsible for payment processing

6. Payment History: Add for recurring invoices or when showing payment status of previous invoices

1. Schedule A - Itemized Breakdown: Detailed breakdown of charges, hours, or quantities when the main invoice contains summary information only

2. Schedule B - Supporting Documentation: Additional documentation such as timesheets, delivery receipts, or work completion certificates

3. Appendix 1 - Terms and Conditions: Detailed payment terms, late payment policies, and dispute resolution procedures

4. Appendix 2 - Tax Calculations: Detailed breakdown of tax calculations for multiple jurisdictions or complex tax scenarios