Invoice Template with Auto-Calculations

Help me create a professional invoice template in Excel:

**Business Details:**
- Business type: [freelance / small business / company]
- Industry: [for context on line items]
- Currency: [USD, EUR, GBP, etc.]

**Invoice Structure:**
- [ ] Company logo placement
- [ ] Business contact info
- [ ] Customer billing/shipping address
- [ ] Invoice number (auto-generate)
- [ ] Invoice date and due date
- [ ] Payment terms
- [ ] Line items with descriptions
- [ ] Tax calculation
- [ ] Discounts
- [ ] Payment instructions
- [ ] Notes/terms section

**Calculation Requirements:**
- Tax rate: [e.g., 10%]
- Multiple tax rates: [Yes/No]
- Tax-inclusive or exclusive pricing: [specify]
- Discount type: [percentage / fixed / per line item]
- Shipping charges: [Yes/No]

**Automation Needs:**
- [ ] Auto-increment invoice number
- [ ] Calculate due date from terms
- [ ] Lookup customer info
- [ ] Product/service price lookup
- [ ] Running balance tracking

**Additional Features:**
- [ ] Multi-currency support
- [ ] Partial payment tracking
- [ ] Convert to PDF
- [ ] Email integration

Please provide:
1. Invoice layout design
2. Key formulas for calculations
3. Auto-numbering system
4. Data validation for entries
5. Print optimization
6. Best practices for professional invoices