Guides

The generators on this site produce a document — an invoice, a receipt or a quote, drawn into a PDF on your own device. The guides explain what is underneath it: the arithmetic that turns a column of lines into a total, and the conventions the arithmetic cannot settle. A document is checked by someone holding a calculator; these pages exist so the figures and the labels survive that check.

Every money figure in a worked example is computed when the page is built, by the engine the generators run. Take a fictional invoice with two lines — 3 site visits at $85.00 each and 1 replacement filter at $40.00 — a 10% discount, and tax of 8% added on top. The engine prints the lines as $255.00 and $40.00, a subtotal of $295.00, a discount of $29.50, tax of $21.24 on the discounted base of $265.50, and a total of $286.74. None of those numbers was typed; the methodology page is the vetted account of every rule behind them.

The guides are not tax advice: the engine applies the rate you type in the mode you choose, and no page here decides whether a sale is taxable, at what rate, or what a document must carry where you trade. They are not accounting either: nothing is stored, tracked or filed.

Invoice vs. receipt vs. quote

Three documents that are nearly the same page of paper and make three different claims about money: an invoice requests payment not yet made, a receipt confirms payment that has, a quote prices work not yet agreed. The guide walks the usual sequence from quote to receipt, shows where deposit work runs the loop twice, places the proforma invoice, and settles the choice by which of the three claims about money you are making.

Receipts, quotes, and the bottom-line label

What the last line is called is set by the document type: “Balance due” on an invoice, “Amount paid” on a receipt, “Quote total” on a quote. The guide builds a fictional invoice, receipt and quote from the same lines and shows what each prints, why the wording follows the document — a receipt reading “Balance due” invites a second payment, and a quote reading it demands money not yet owed — and why the amount-paid field moves an invoice's balance but is left out of the other two.

What to put on an invoice

A field-by-field reading of the generator's form, written for the person who was not in the room when the work was agreed: the name that should match the account being paid, a number unique across everything you have issued, two dates doing two jobs, line descriptions a client can recognize, the three tax settings, and the notes field where payment instructions go. It stops where your own jurisdiction's requirements begin.

How invoice totals are computed

Money is held in whole cents because binary floating point cannot represent 0.1 exactly; each line is quantity × unit price rounded once, half away from zero, so the printed lines add up to the printed subtotal; then subtotal → discount → taxable base → tax → shipping → total → amount paid → balance due, in that order. Each step is walked through on fictional documents — multi-line, discounted, taxed in both modes, with shipping, overpaid to a zero balance, discounted to the floor — every figure computed by the engine.

Inclusive versus exclusive tax arithmetic

Tax added on top is multiplication; tax already inside a price is found by dividing by 1 + the rate, never by subtracting a percentage. On a fictional line of $120.00 marked tax-included at 20%, the engine finds $20.00 of tax and leaves the total at $120.00; subtracting 20% would print $24.00, overstating the tax by a fifth. The guide shows the error at several rates, covers the mode with no tax line, and is explicit about what the engine does not decide: which mode applies to you.

Sales tax vs. VAT

The two shapes tax takes — added at the point of sale to a price advertised without it, or already inside a price shown tax-inclusive — and why the second is the one that goes wrong by hand. The guide gives the divide-not-subtract rule in head-checkable form with a build-time check behind it, maps the generator's three modes to the price you actually quoted, and is plain that the tool applies the rate you type and nothing more.

How to number invoices

A number has one job: letting two people with two pieces of paper agree on which document they mean. Four schemes — plain sequential, year-prefixed, per-client, date-based — and what each costs; why a gap is ambiguous and a reused number is worse; why a counter starting at 1 tells the client how many invoices you have ever issued; and why, since the tool stores nothing between visits, the register is yours to keep.

Payment terms

Net 30, due on receipt, end-of-month, 2/10 net 30, deposits and part payment — what each phrase means, and the ambiguity in all of them: thirty days from what? The guide's answer is a calendar date in the due-date field with the phrase in the notes, and it shows where the amount-paid field records a deposit already received. Late fees: the guide says why they belong in the agreement, and that the tool applies none of its own.

Where to go next

The invoice generator, receipt generator and quote generator are three versions of one form, each ending with the line its document type calls for. The methodology page is the single vetted statement of every rule the engine applies and every limit it stops at, and the about page says who publishes this and why it works without an account.

A document generator, not accounting or tax advice. Nothing you enter leaves your browser, and nothing is stored — download the PDF before closing the tab. How every figure is produced is set out on the methodology page.