The question is usually "how much of it", not "can I"
People approach expenses as a yes or no list, and most real costs are not on either list. They are part business and part personal, and the claimable amount is the business proportion.
gov.uk puts it plainly: you can only claim allowable expenses for the business costs. Then it works the example that makes it obvious.
Home costs, and a method you can defend
Working from home is the same principle with an extra step. gov.uk works it through: electricity of £1,120 divided across four rooms gives £280 for the room you work in, and that is then adjusted down again if you only work there part of the week.
What matters is that the method is reasonable and consistent. Rooms and hours is the usual pairing, and any defensible basis applied the same way each year is better than a generous one you cannot explain.
There is also a simplified flat rate based on hours worked at home. It is less generous and it takes a minute rather than an evening, which for a lot of people is the right trade.
The three that no apportionment will save
Most costs scale down to a business share. These do not, and they are the three people try hardest to claim.
- Ordinary clothing. gov.uk is explicit that you cannot claim the costs of normal clothing, even if you wear it for work. Protective clothing and a genuine uniform are a different matter.
- Client entertaining. Disallowed outright, with no share claimable on the basis that business was discussed, and it reaches the travel costs incurred in connection with it too.
- Ordinary commuting. Travel between home and a permanent workplace is not allowable, and neither is what you buy to eat on the way.
That last one has an important other half, and it is where money gets left behind rather than over-claimed. Travel to a temporary site, to a customer, or between jobs is a different thing and is claimable. For anybody working across several locations it is usually the biggest number on the return, and it is routinely under-claimed by people who have heard "you cannot claim your commute" and stopped there.
The strict test is stricter than the guidance sounds
The plain guidance talks about business costs and proportions. The underlying legal test is tighter than that, and where a cost has a genuine dual purpose that cannot be separated, the whole thing can fail rather than splitting.
Which is why the clothing example works the way it does. It is not that a suit is only partly for work, it is that you have to be dressed regardless, so there is no business-only slice to carve out. If a cost cannot be cleanly divided, do not assume a percentage will be accepted.
Keeping the evidence, which is the part that fails later
The difficulty at an enquiry is almost never proving that money left the account. It is proving what it left for, years afterwards, when nobody remembers.
So the habit worth having costs nothing: note the reason at the time. A bank line reading a supplier name and a figure is weak on its own; the same line with three words of context is fine.
Where the expenses end up
Expenses reduce the profit the tax is charged on, so this feeds straight into the Self Assessment estimate, which covers the bill itself and the payment on account that makes the first January larger than people expect.
Mileage has its own system rather than being a proportion of your running costs, and the mileage claim calculator handles it, including the rate threshold and what actually counts as a business mile. And if the answer to all this is that you are not sure you should be filing at all, do I need to file a tax return is the prior question.
Common questions
Can I claim something I use for both work and personally?
You can claim the business proportion of it, which is the answer people miss because they are looking for a yes or a no. HMRC gives the example of a £200 phone bill made up of £130 of personal use and £70 of business use: you claim the £70. The same logic covers a vehicle, a laptop or a broadband connection. What you cannot do is claim the whole cost because part of it was for work, and that is the single commonest error in a set of self-employed accounts.
How do I work out the business share of my home costs?
By using a reasonable method of dividing the costs, which usually means splitting by the number of rooms and then by the time actually spent working. gov.uk works an example: electricity of £1,120 across four rooms gives £280 for the room you work in, and that figure is then adjusted down again if you only work there part of the week. Any consistent, defensible method is acceptable. There is also a simplified flat rate based on hours worked, which is less generous and far quicker.
Can I claim my work clothes?
Not if they are ordinary clothing, even when you only ever wear them for work. gov.uk is explicit that you cannot claim the costs of normal clothing. Protective clothing and a uniform are different, and so is anything that is genuinely unusable outside the job. The test is not whether you personally would choose to wear it socially, which is why buying a suit for client meetings does not become claimable by never wearing it anywhere else.
Can I claim taking a client for lunch?
No. Client entertaining is disallowed outright, and it is one of the few areas with no apportionment available at all: you cannot claim a share of it on the basis that business was discussed. That includes hospitality at events, and it also reaches the travel costs incurred in connection with the entertaining. Staff entertaining sits under different rules, which is why the two get confused.
Can I claim the drive to work?
Not for ordinary commuting. Travel between home and a permanent workplace is not allowable, and neither is subsistence bought on those journeys. Travel to a temporary site, to a customer or between jobs is a different matter and is claimable, which is why the distinction is worth getting right rather than assuming either extreme. For anybody working from several locations it is usually the largest expense on the return and the one most often under-claimed.
Do I need receipts for everything?
You need to be able to show what you spent and why, and a receipt is the easiest way to do it. The record matters more than the format: a bank statement line with no explanation is weak evidence years later when nobody remembers what it was. The practical habit that costs nothing is noting the reason at the time, because the difficulty at an enquiry is almost never proving the money left the account, it is proving what it left for.