Invoice & Billing Calculator
Calculate invoice totals with tax, discounts, and multiple line items. Generate a quick invoice summary.
📋 Business📐 Invoice Total = Subtotal × (1 + Tax Rate) - Discount
Item 1 price ($)
Item 2 price ($)
Item 3 price ($)
Tax rate %
Discount %
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Invoice & Billing Calculator | Invoice Total = Subtotal × (1 + Tax Rate) - Discount | $ total |
Step-by-Step Examples
Example 1
Web Design Invoice
$1,500 design + $800 dev + 8% tax.
- Subtotal: $2,300 | Tax: $184
- Total: $2,484
✓ $2,484
Example 2
With Discount
$5,000 project, 10% discount, 0% tax.
- Subtotal: $5,000 | Discount: $500
- Total: $4,500
✓ $4,500
Example 3
Consulting + Expenses
$3,000 consulting + $450 expenses, 8% tax.
- Subtotal: $3,450 | Tax: $276 | Total: $3,726
✓ $3,726
Real-World Applications
Freelancers
Quickly calculate invoice totals.
Consultants
Add tax and discounts to project fees.
Small Businesses
Calculate correct invoice amounts before sending.
Clients
Verify invoice totals before paying.
Common Mistakes to Avoid
⚠️
Applying tax before discount
Always calculate discounts on the pre-tax subtotal first, then apply tax to the discounted amount.
⚠️
Not including all line items
Missing reimbursable expenses (travel, software licenses, printing) from invoices leaves money on the table.
Frequently Asked Questions
When should I send invoices? ▾
Service businesses: immediately upon completion or milestone. Monthly retainers: first of each month. Projects: 50% deposit upfront, 50% on delivery is common.
Net 30 vs net 15 payment terms? ▾
Net 30 (30-day payment) is standard B2B. Net 15 or 'due on receipt' for smaller freelancers. Offering 2% discount for payment in 10 days (2/10 net 30) can accelerate cash flow.
How to handle late invoices? ▾
Charge late fees (1-2% per month is common). Send automated reminders at 7, 14, and 30 days overdue. Consider requiring deposits upfront for new clients.