Invoice HopThe order of the math
Invoice totals go wrong when steps happen in a different order. This calculator always works the same way: each line is quantity times price, lines add up to the subtotal, the discount comes off the subtotal, tax is charged on what remains taxable, and payments received come off the total.
| Step | Formula | Result |
|---|---|---|
| Line 1 | 3 × $95.00 | $285.00 |
| Line 2 | 1 × $62.00 | $62.00 |
| Subtotal | $285.00 + $62.00 | $347.00 |
| Tax (part only) | $62.00 × 8.25% = $5.115 | $5.12 |
| Total | $347.00 + $5.12 | $352.12 |
How a discount and taxed lines work together
When only some lines are taxed and the invoice has a discount, the discount is spread across all lines by the same percentage before tax. So a 10% discount lowers the taxed lines by 10% too. That keeps you from charging tax on money the customer is not paying.
Same job with a 10% discount
- Subtotal: $347.00
- Discount 10%: −$34.70
- Taxed part after discount: $62.00 × 90% = $55.80
- Tax: $55.80 × 8.25% = $4.6035, rounded to $4.60
- Total: $347.00 − $34.70 + $4.60 = $316.90
Some states treat discounts and tax differently, especially manufacturer coupons. Check with your accountant if a big share of your work is taxable.
Partial payments and the balance due
If the customer paid a deposit or part of the bill, enter it under payments received. The calculator subtracts it from the total and shows the balance due. Keep each payment’s date and method in your records, because the customer will ask what they already paid when the next reminder arrives.
Example: a $2,430.00 invoice with $1,000.00 paid by Zelle leaves a balance of $1,430.00. In the Invoice Hop app, each payment you record also creates a receipt that shows the remaining balance.
The CSV download lists every line, the subtotal, discount, tax, total, payments and balance, so you can paste the result into a spreadsheet or send it to your accountant.
Questions
How does the calculator round?
Each line is rounded to the cent, and tax is calculated on the taxable amount and rounded to the cent once. Halves round up.
Can I tax only some lines?
Yes. Choose “Only lines I tick” and tick the taxable lines. The discount percentage is applied to taxed lines before tax.
Does it save my numbers?
No. Nothing is stored or uploaded. Download the CSV if you want to keep the result.
What sales tax rate should I use?
It depends on your state, county and city, and on what you sell. Check your state’s department of revenue or ask your accountant.
Not tax or legal advice. This page is general information. Tax, payment and collection rules differ by state. Ask a qualified accountant or attorney about your situation.