Two different claims
An invoice says “you owe this”: it has an issue date, usually a due date, payment terms, and a balance that is still outstanding. A receipt says “this was paid”: it has the amount received, the method, and no due date because nothing is owed. The fields overlap enough that people use one for the other, which causes a paper trail that does not match the money.
| Field | Invoice | Receipt |
|---|---|---|
| Number and date | Yes | Yes |
| Seller and buyer details | Yes | Seller; buyer usually anonymous at a counter |
| Lines, quantity, price | Yes | Yes |
| Tax | Yes, if applicable | Yes, if applicable |
| Due date / terms | Yes | No |
| Amount paid / change | Deposit only | Yes |
The order of the arithmetic
Both documents apply the same arithmetic in the same order, and the order changes the numbers. Measured with the calculator this site uses: two lines of 2 × 120 and 1 × 80 give a subtotal of 320; a discount of 20 is subtracted before tax; a 20% tax on the discounted amount is 60; the total is 360; a deposit of 100 leaves a balance of 260.
| Step | Invoice example | Receipt example |
|---|---|---|
| Subtotal | 320.00 | 9.00 |
| Discount | −20.00 | — |
| Tax | 20% → 60.00 | 10% → 0.90 |
| Total | 360.00 | 9.90 |
| Deposit / tendered | 100.00 deposit → balance 260.00 | 20.00 tendered → change 10.10 |
The receipt's rows are 2 × 4.50. Tax is applied to the subtotal, and change is tendered minus total, floored at zero; a shortfall is shown as a balance due, not as negative change.
Numbering and records
A document number should be unique, sequential and never reused. A workable scheme is a prefix, the
year and a zero-padded counter, such as INV-2026-0042 — the format this site's numbering
helper returns. The counter lives in your records, not in the page: the tool stores nothing, so it
cannot know which number you used last. A gap in a sequence is easier to explain than a duplicate.
For an invoice, keep the issued document and a record of payments against it; the balance is a running figure, not a property of the original file. For a receipt, keep the paid document and note any refund or correction separately. A reissued receipt should normally be marked as a duplicate, because two identical receipts can look like two payments.
Payment terms and late payment
An invoice's due date is a contractual term, not a calculation. “Net 30” means thirty days from the issue date; “2/10 net 30” means a 2% discount if paid within ten days, otherwise the full amount in thirty. The form has a date field and a discount field, but it does not interpret the terms for you: enter the due date and the discount you are prepared to accept, and state the terms in the notes so the buyer sees the same rule you applied.
A receipt for a card payment should show the method (card, cash, transfer), the amount tendered and the change where cash is involved, and the last four digits or a reference where a card is used. Those fields are what make a receipt useful in a dispute; the line items alone do not prove how the money arrived. The receipt generator has a payment-method field for exactly this reason.
Currency and rounding
One document, one currency. The currency selector changes the symbol and the formatting, not the arithmetic; converting between currencies is a separate decision with its own rate and date, and it should not be hidden in a document that claims a fixed total. Rounding follows the jurisdiction: this engine rounds each amount to the minor unit, which is the common default, but invoices that round at the line level and those that round the total can differ by a cent.
Tax is a rate you supply
The calculators apply a single rate to the discounted subtotal, which matches the common “tax on the net amount” rule. They do not know your jurisdiction, whether prices are tax-inclusive, or how your tax authority requires rounding. Mixed-rate documents — zero-rated and standard-rated lines together — need a rate per line, which these forms do not model. Split the document by rate, or use accounting software, rather than burying the difference in a note.
Rounding is the other local convention. The engine rounds each amount to cents before formatting; invoices that round per line and those that round the total can differ by a cent, and some jurisdictions prescribe one. The arithmetic here is a correct default, not a substitute for the rule that applies to you.