23/07/2026
What really happens if you get it wrong.
For a lot of business owners this is the quiet worry that sits in the background all year. So here is the honest version, without the scare stories.
First, the part that is genuinely unforgiving.
File your tax return late and there is an automatic £100 penalty, even if you owe nothing at all. Leave it three months and daily charges of £10 start, running up to a maximum of £900. At six months there is another penalty of £300 or 5% of the tax due, whichever is higher, and the same again at twelve months.
It is also worth knowing that filing and paying are two entirely separate things. Late payment charges sit on top of late filing ones, and interest runs daily until the bill is cleared. So even if the money is not there yet, file on time. It stops half the problem in its tracks.
Now the reassuring part, and it is the bit nobody ever tells you.
If you took reasonable care and still got something wrong, HMRC will not usually charge a penalty at all. You pay the tax that was owed and you move on. And "reasonable care" is judged against your own knowledge and circumstances, not against what an accountant would be expected to know.
There is one more thing that makes an enormous difference. If you spot an error and tell HMRC before they find it, a careless mistake can carry no penalty whatsoever. Wait until they come to you, and that same error starts at 15%. Identical mistake. Completely different outcome. Being upfront is the single biggest lever you have.
Which brings us to the real point. The danger was never making the mistake. It is hiding it. Honest slips are cheap to put right. Deliberate ones are not, and the penalties climb steeply once HMRC decides something was concealed on purpose. Almost every horror story you have ever heard started with someone saying nothing and hoping it would go away.
So if something has been nagging at you, say it out loud. We have never once judged anyone for a mistake. We just fix it early, while it is still small and still cheap.
There are no silly questions here. Fixed monthly fee, 24 hour response, and no jargon.
Book a free discovery call: https://tidycal.com/dorota