Frequently asked questions
Everything below is answered somewhere on this site. The first four sections collect the questions attached to each tool; the last covers the tools themselves — where your data goes, what the download actually is, and what these tools deliberately do not do.
Last reviewed 17 Sep 2026.
Invoice generator
Open the invoice generator — the same questions, in context, with the tool in front of you.
Is my invoice data uploaded anywhere?
No. The form runs entirely in your browser, the draft is saved to localStorage on your own device, and the PDF is generated locally by your browser. Nothing is transmitted to a server, so there is no account to create and no data for us to lose.
Can I use this if I am not registered for VAT, GST or sales tax?
Yes. Leave the tax rate at 0 and the tax row disappears from the PDF. Do not invent a tax line or a registration number you do not hold - charging tax you are not registered to collect is a serious problem in every jurisdiction.
What invoice number should I start with?
Anything sequential and consistent. INV-2026-0001 is a good default: the year makes filing obvious and the four-digit counter sorts correctly up to 9,999 invoices. What matters is that you never duplicate or skip a number afterwards.
How do I invoice a client in another currency?
Pick their currency in the dropdown before you enter amounts. The symbol updates across the form, the totals panel and the PDF. Agree the currency in writing beforehand, and remember that your bank, not this tool, sets the conversion rate you actually receive.
Can I add my logo, and what formats work?
Upload a PNG or JPEG up to 512 KB. It is converted to a base64 data URL and embedded directly in the PDF. SVG and WebP are not supported by the PDF engine, and the size cap exists because the logo is stored alongside the draft in localStorage.
Where is my draft saved, and how do I clear it?
In your browser, under a key beginning with invoicemaker:v1: (this tool uses invoicemaker:v1:invoice-generator). Use "Clear saved draft" to wipe it and reset the form. The draft is per-browser and per-device, so it will not follow you to another machine.
Profit margin calculator
Open the profit margin calculator — the same questions, in context, with the tool in front of you.
What is the difference between margin and markup?
Both measure the same profit. Margin divides it by revenue, markup divides it by cost. Margin is always the smaller percentage. A 100% markup equals a 50% margin, and a 25% markup equals a 20% margin.
What is a good profit margin for a freelancer or small studio?
For time-based service work with few direct costs, 50-70% gross margin is typical and 20-35% net margin is healthy. Businesses that resell hardware, media or print run structurally lower percentages on much larger revenue, which is normal rather than a problem.
Should my own salary count as a cost?
For gross margin, no - your time is what you are selling. For a realistic net margin, yes: put a market salary for the hours you personally worked into overheads. Otherwise the business looks profitable only because you are working for free.
How do I price a project to hit a 40% margin?
Divide cost by 0.6. A 3,000 cost needs a 5,000 price. Multiplying by 1.4 gives 4,200, which is a 28.6% margin - the single most common pricing error in freelance quoting.
Do Stripe or PayPal fees belong in cost or overheads?
In cost, because they scale with the invoice. A percentage of the amount plus a small fixed fee can consume a tenth of a thin margin, so include them before you agree to a discount. Take the exact rate from your own provider - it varies by country, card type and plan, and it changes.
Tax, VAT and GST calculator
Open the sales tax, vat & gst calculator — the same questions, in context, with the tool in front of you.
Why can I not just subtract the percentage from the gross total?
Because the percentage was applied to the smaller net figure, not to the gross. Removing 20% of the gross removes 20% of a bigger number. Divide by 1.20 instead, or multiply the gross by rate / (100 + rate) to get the tax directly.
Which rate should I use?
The rate for the place of supply, which is usually where your customer is rather than where you are. UK standard VAT is 20%, Australian GST is 10%, Indian GST is commonly 18%, and much of the Gulf uses 5%. US sales tax is set state and city by city, so use Custom.
Do I charge tax to a client in another country?
Often not, but the rules are specific. Cross-border B2B services within the EU typically shift the liability to the buyer under the reverse charge, and exports are frequently zero-rated. Confirm the treatment for your own registration before you invoice.
Should tax be rounded per line or per invoice?
Both are accepted in most jurisdictions, and both must be applied consistently. This tool rounds once against the base you enter, which matches invoice-level rounding. A one or two penny difference against per-line software is expected, not an error.
Are VAT, GST and sales tax the same thing?
Mechanically VAT and GST are near-identical: collected at each stage with input tax reclaimable. US sales tax is a single-stage tax on the final sale and is generally not reclaimable by the buyer. The arithmetic in this calculator is the same for all three.
Late payment fee estimator
Open the late payment fee estimator — the same questions, in context, with the tool in front of you.
How much late interest can I legally charge?
It depends on your jurisdiction and on what your contract says. UK statutory interest on commercial debts is 8% above the Bank of England base rate plus fixed compensation; the EU floor is eight points above the reference rate plus at least 40 euro; US limits are set per state. Check your own rules before enforcing a rate.
Should I use simple or compound interest?
Simple interest is easier to explain, easier to defend and is what most statutory schemes use. Compound is defensible only if your signed contract says so explicitly. Over sixty days the difference on a five-figure invoice is usually a few pounds or dollars.
Do I need a late fee clause in my contract to charge one?
A written clause makes collection dramatically easier, and in some places it is required. Several jurisdictions also grant a statutory right to interest on commercial debts even without a clause - but you will still be arguing about it, which a single sentence in the agreement avoids.
Is a flat fee or percentage interest better?
A flat fee is more effective on small invoices, where a percentage is too small to notice. Percentage interest works better on large balances and long delays. Many contracts use both: a fixed administrative charge plus daily interest, which is exactly what this estimator models.
Is late payment interest taxable, and does it carry sales tax?
Interest is normally taxable income to you. In most VAT and GST systems, interest charged for late payment is outside the scope of the tax because it is compensation rather than consideration for a supply - but confirm the treatment locally before adding it to a tax-bearing line.
About the tools
These are the questions that come up about the site rather than about a particular calculation. They are the ones that decide whether a tool is worth using at all, so they are answered in full.
Is my invoice data uploaded to a server?
No. The form, the totals, the logo and the PDF are all produced in your browser. There is no account, no backend to sign in to, and no copy of your draft on our side, which is also why we could not lose it. The draft lives in your browser storage and the PDF is generated locally.
Why does my draft disappear if I clear my browser data?
Because the draft is stored in this browser, on this device, and nowhere else. Clearing site data, using a private window, or switching to another browser or machine all start from an empty draft. That is the trade for having no server holding your client details. Download the PDF when you are happy with it, and it will outlast the draft.
What format is the downloaded file, and will my accountant accept it?
A PDF, drawn as vector text and shapes rather than an image of a screen. That means it is small, selectable, searchable, and stays sharp when printed or zoomed, and it imports as a document into accounting packages such as Xero, QuickBooks and FreeAgent rather than as a picture needing manual re-entry. It is not a machine-readable e-invoice, so if your jurisdiction or client requires one - UBL, Factur-X, Peppol and so on - you will still need software that produces it.
Which currencies and tax systems are supported?
A long list of currencies, and a tax rate you choose yourself with the label you want printed on it: Sales Tax, VAT, GST, Service Tax, or plain Tax. The generator does the arithmetic on the rate you enter. It does not know your registration obligations, your place of supply, or whether a transaction is exempt or zero-rated, and it is not meant to.
Is the PDF accessible or screen-reader friendly?
The site is built to be keyboard navigable and respects your reduced-motion and colour-scheme preferences, and the forms have real labels. The generated PDF is a different matter: it is laid out as positioned text on a page, which is the right choice for a document that has to print identically everywhere, but it is not a tagged accessible PDF. If accessibility of the output document matters for a specific client, check it before you rely on it.
Can I use the documents commercially, or put my own logo on them?
Yes, and putting your own logo on them is the intended use. The tools are free to use for your own invoicing, whatever you charge for your work. There is no attribution requirement and no watermark. What you should not do is present the site or the generated documents as your own product, or imply it is a bespoke system built for your business.
Is this a substitute for accounting software?
No, and it is not trying to be. There is no double-entry bookkeeping, no reconciliation, no bank feed, no multi-user access and no reporting, and a spreadsheet will beat it at all of those. What it does is produce a correct, professional document quickly, and do a few pieces of arithmetic that are easy to get wrong, without asking you to pay for a subscription or hand over your client list first.
Why does the site have adverts?
Because it is free, has no paid plan, stores nothing about you, and takes no payment details. Advertising pays for the hosting. It is kept to a small number of clearly labelled slots so it does not interfere with the tools, and it never appears inside a form or between a question and its answer.
Didn’t find your answer?
Email support@invoicemaker.website. If something is calculating the wrong number, include the tool, the exact values you entered and what you expected to see — a report with the numbers in it is usually answerable on the first reply.
If the answer is more of an explanation than a fix, the guides probably cover it properly, and the glossary will tell you what a term means.