Duplicate invoice book or an app: what the carbon copy gets right

What does a duplicate invoice book get right?

Three things, and any app should be judged against them. Every page has a number, so no two invoices share one. One writing makes two copies, so the customer takes one and you keep the other. And it works anywhere, because there is nothing in it to run out of battery or signal.

A duplicate invoice book is a pad of numbered pages in pairs: a white top sheet and a coloured copy underneath. Most are carbonless now, which means the back of the top sheet is coated so that the pressure of your pen marks the page below. There is no loose carbon paper, but the result is the same. What you write once appears twice.

A triplicate book adds a third copy, usually for an office or a supplier. If the invoice only goes between you and the customer, duplicate is the one you want.

The third job is why the book has lasted. A kitchen with no reception, a loft, a farm at the end of a track: the book does not care where you are standing when the work is done.

What does the paper version cost you?

Very little on the day. The cost turns up later: in the sums, in the copy you cannot send again, in the invoices nobody has paid, and at the end of the year, when the book has to become figures somebody can use.

The sums are yours

Every total on a handwritten invoice is mental arithmetic done standing up. Multiply a line wrongly or add VAT to the wrong figure and the mistake goes out on the customer's copy, and the carbon keeps exactly the same mistake.

The customer's copy is the only one

The top sheet goes into a kitchen drawer. Six weeks later the customer asks for it again, and you are photographing a carbon copy on the van's dashboard.

Nothing tells you who has not paid

The book records what you invoiced. Whether each one was paid lives in your head or in ticks down the margin, and finding the three that are overdue means leafing back through the stubs.

The book is the record

GOV.UK says a self-employed person keeps records for at least five years after the 31 January deadline for the tax year they belong to. That makes a shelf of books, each one the only copy, and every year somebody types the stubs into a spreadsheet or hands the lot to whoever does the books.

The book costs almost nothing on the day. It sends its bill at the end of the year.

If Making Tax Digital for Income Tax applies to you, your records also have to be digital, which a book is not. Who it applies to, and from when, is in the self-employed expenses guide.

Can a phone do the same three jobs without signal?

Two of them completely, and the third nearly. Invoice Koi numbers the invoice and draws it on the phone, so neither needs a connection. Putting the customer's copy in their hand with no signal is the one place a carbon is still quicker.

A number on every invoice

A draft has no number. The number arrives when you issue the invoice, it comes from a counter kept on the phone, and it is never given out twice, even if that invoice is later deleted. That is the book's own rule: a spoilt page stays in it, marked void, rather than being torn out and its number used again.

Two copies from one writing

Your copy is the one on the phone, with the client, the lines and the totals worked out for you. The customer's copy is a PDF, and there are three ways to hand it over. Send it, which needs whatever connection your mail or messages app needs. Print it, if there is a printer the phone can reach. Or, standing next to them, use AirDrop on an iPhone or Quick Share on Android, which pass a file from phone to phone without signal when both phones support it.

If none of those works where you are standing, the invoice is finished and waiting, and it goes the moment you have a bar of signal.

Signed on the doorstep

Tap "Collect client signature" and hand the phone across. The customer signs on the screen, and the invoice prints their mark under "Agreed and signed by", with their name and the date beside it: the same thing a signature on the top sheet does when it comes through on the carbon.

The custom book

A custom invoice book has your name and details printed at the top of every page. On the phone that is your logo and business details, set once and printed on every invoice after it.

What about a receipt book?

A receipt book is the same pad for a different moment: when the money arrives. GOV.UK puts the difference in one line: "An invoice is not the same as a receipt, which is an acknowledgement of payment."

In Invoice Koi the receipt is the invoice itself, once it has been paid. Tap "Record a payment" on the invoice, put in what came, when and how (cash, a transfer, a cheque), and the PDF gains a "Paid" section listing each payment, with the balance beneath it. Send that and the customer has their receipt.

A deposit and then the rest work the same way: two payments against one invoice, and nothing to match up between two different books afterwards.

When is the book still the better answer?

When you write a handful of invoices a month, your customers pay on the spot and like a piece of paper, and you have no wish to pay for software. A book is cheap and quick, and nobody needs to learn it.

If that is you, keep it, and make it a good one. Numbered pages. Duplicate rather than triplicate, unless somebody else needs the third copy. And your name, address and contact details printed or stamped at the top, so you are not writing them out on every page.

Whichever you use, the invoice needs the same details. The sole trader invoice guide lists them, and the simple invoice example shows one filled in.

The test for switching is the one this page started with. Turn off your phone's signal, write a real invoice on it, and see whether it does the three jobs your book does. If it does not, the book is still the better tool.

Asked about invoice books