When the laptop with your business on it dies
A question worth answering before you need to: if the laptop you write your invoices on stopped working this afternoon, what would you have lost?
Most people have never checked. The honest answer for a lot of one person businesses is several years of quotes, customer details, prices and paperwork, some of which they are legally required to be keeping.
Where things actually are
Start by finding out, because assumptions here are usually wrong.
Anything in a desktop program is on that machine. Spreadsheets in a Documents folder are on that machine. A cloud drive folder is on that machine and on a server, which is genuinely different. Anything in a web application is on somebody else's server and reachable from anywhere. And anything in a browser based app that stores data locally is on that machine, in that browser, whatever the address bar suggests.
That last one catches people, because it looks like a website. The test is simple: turn the wifi off and open it. If it still works fully, the data is local, and local has real advantages along with a specific fragility.
The three ways it goes
Hardware failure is the obvious one and the least common. Drives do fail, and modern ones tend to fail without warning rather than with the clicking noises people expect.
Theft and loss are more common than failure, particularly for a van based trade, and they take the machine and the data together.
The one that actually gets people is deletion, and it is the least dramatic. Clearing browser data because something was misbehaving. A phone reset. A laptop wiped and reinstalled by a shop, or by a family member being helpful. Nothing broke. The data simply is not there any more, and there is no support desk anywhere that can retrieve it, because they never had it.
What a backup has to be to count
Three properties, and a copy missing any of them is not a backup.
Somewhere else. A second copy on the same laptop protects you from deleting a file and from nothing else.
Recent enough that losing the gap would be annoying rather than serious. Weekly is fine for most trades. A year old backup is an archive.
Restorable, which means you have actually tried it. An untested backup is a belief, and the point where you find out it was only ever a belief is the worst possible point.
A routine that survives being busy
The best backup routine is one you have no part in. If your tool syncs to an account, that is a second copy maintained without you remembering anything, and it covers hardware failure, theft and most deletion.
But sync is not a backup on its own, and it is worth being clear why. Sync propagates. Delete a customer on Tuesday and the sync obediently deletes them everywhere. What sync protects against is losing a device. What it does not protect against is losing data, and those are different accidents.
So the second layer is a file you hold: an export, taken on a schedule, kept somewhere the running system cannot reach. Once a month is enough for most people. Put it with the Friday admin on the first Friday, keep the last three, and delete older ones so the folder stays legible.
Then test one. Once, this year. Open it, or import it into a fresh install, and confirm it contains what you think. Twenty minutes, once, and the belief becomes knowledge.
The records you are required to keep
This is the part with a legal edge rather than only an inconvenient one.
A sole trader has to keep records for at least five years after the January submission deadline, which in practice means around six years of invoices, receipts and the paperwork behind them.
Six years is longer than most laptops last and considerably longer than most phones. Which means a record keeping system that lives on one device is not merely fragile, it is incapable of meeting the requirement, because the device will be replaced twice inside the period.
The convention worth borrowing
People who do this for a living use a rule of thumb: three copies of anything that matters, on two different kinds of storage, with one of them somewhere else entirely.
For a one person trade that translates into something quite ordinary. The working copy on your laptop or phone. A second maintained automatically, by syncing to an account or to a cloud drive. And a third you export yourself and keep somewhere the first two cannot reach, which matters because the failure that gets people is deletion, and deletion propagates through anything that syncs.
The third copy is the one that feels excessive and is the one that saves you. Sync protects against a device dying. Only a separate copy protects against you, or a helpful family member, or a browser clearing its storage because it needed the space.
None of this needs buying anything. A monthly export into the cloud drive you already pay for satisfies all three, and takes about two minutes.
Answering the question
Go and find out where each thing lives. Quotes and invoices. Customer details and prices. Photographs of work. Certificates. Receipts.
For each one, ask where the second copy is. Anything with no answer is something you are one accident away from losing, and most of them are fixed in an evening: a folder moved into a cloud drive, an export taken, an account signed into that you had been meaning to set up.