A professional invoice needs specific fields to be legally valid and to get paid on time. Missing information is one of the most common reasons payments are delayed — clients use incomplete invoices as justification to push payment past the due date.
What every invoice must include
Required fields
- Invoice number: Unique sequential identifier (INV-001, INV-002…)
- Issue date: When the invoice was created
- Due date: When payment is expected
- Your business details: Name, address, email, phone
- Client details: Name/company, address, email
- Line items: Description, quantity, unit price, amount
- Subtotal: Sum of all line items before tax
- Tax: VAT/GST if applicable
- Total: Final amount due
- Payment terms: How to pay (bank transfer, PayPal, etc.)
Optional but professional
- Logo — significantly increases the perception of professionalism
- Purchase order number — required by many larger companies
- Late payment policy ("1.5% per month after due date")
- Thank you note
Invoice numbering systems
Keep invoice numbers sequential and never reuse them. Common formats:
| Format | Example |
|---|---|
| Sequential | INV-001, INV-002, INV-003 |
| Year-based | INV-2025-001, INV-2025-002 |
| Client-based | ACME-001, ACME-002 |
| Date-based | INV-20250412-001 |
The format doesn't matter — consistency does. Use the same system throughout and your accounting will thank you.
Payment terms explained
| Term | Meaning |
|---|---|
| Net 30 | Payment due 30 days after invoice date |
| Net 15 | Payment due 15 days after invoice date |
| Net 7 | Payment due 7 days — common for freelancers |
| Due on receipt | Payment due immediately |
| 2/10 Net 30 | 2% discount if paid within 10 days, otherwise 30 days |
Most freelancers start with Net 30 but switch to Net 15 or Net 7 after experiencing late payments. Shorter terms are increasingly accepted, especially for digital services.
Tax on invoices
Tax requirements vary by country and business type:
- Vietnam: Standard VAT is 10% for most goods and services
- EU: VAT rates range from 17% to 27% depending on the country; cross-border B2B sales may be zero-rated
- USA: Sales tax varies by state and is generally not applied to service invoices
- UK: 20% VAT standard rate; you only charge VAT if your business is VAT-registered
If you're unsure whether to charge tax, consult a local accountant. Incorrectly charging (or not charging) tax can create legal and financial problems.
Getting paid faster — proven tips
- Send invoices immediately after completing work, not at the end of the month
- Set shorter payment terms — Net 7 instead of Net 30
- Include multiple payment methods — the easier it is to pay, the faster you get paid
- Follow up on day 1 past due, not day 7 — early follow-up signals you're tracking it
- Add a late payment fee to your terms — even if you never enforce it, it creates urgency
- Use a professional-looking invoice — perceived legitimacy affects payment speed
Common invoicing mistakes to avoid
- No invoice number (makes tracking impossible)
- Wrong client name or address (gives them grounds to dispute)
- Missing payment instructions (surprisingly common)
- Vague line item descriptions ("services rendered" instead of specifics)
- Not keeping copies of sent invoices
How to create a professional invoice for free
- Go to Invoice Generator
- Fill in your business details — they're saved automatically for next time
- Add client information
- Add line items with quantities, unit prices, and tax rates
- Select your currency (20+ supported, including VND with Vietnamese formatting)
- Add payment terms in the notes section
- Choose a template: Minimal, Professional, or Bold
- Click Download Invoice PDF — no watermark, no signup required
Your invoice data is saved in your browser locally and never sent to any server. The live preview updates as you type so you can see exactly how the final PDF will look.