October 21, 2026

Making mistakes with your micro entity accounts can cost you time, money, and sleep. The most common mistakes include missing filing deadlines, incorrectly classifying transactions, failing to meet eligibility criteria, and submitting incomplete financial statements. These errors often happen because small business owners try to handle accounts themselves without full knowledge of HMRC and Companies House requirements. The good news? Most of these mistakes are completely avoidable once you know what to look out for. If you run a small company in the UK, understanding micro entity accounts is not optional. It’s a legal requirement that keeps your business compliant and your finances in order. Let’s break down exactly what these accounts are, the mistakes you need to avoid, and how to fix them before they become expensive problems. Last reviewed: 21 October 2026 Key Takeaways File your accounts at Companies House within 9 months of your year-end, your CT600 with HMRC within 12 months, and pay your corporation tax 9 months and 1 day after year-end. Late Companies House accounts cost £150–£1,500 per year — doubled if you’re late two years running. Late CT600 filing penalties doubled from 1 April 2026 to £200–£2,000. Check your micro entity eligibility every year against the current £1 million / £500,000 / 10-employee thresholds. Keep business records for 6 years and payroll records for 3 years after the end of the tax year. Repay an overdrawn director’s loan within 9 months and 1 day of year-end to avoid the 35.75% S455 tax charge (since 6 April 2026). What Are Micro Entity Accounts? Micro entity accounts are simplified financial statements designed for the UK’s smallest companies. They require less detail than full accounts, which means less paperwork and lower preparation costs. But “simplified” doesn’t mean “simple” when you’re unfamiliar with the process. To qualify as a micro entity, your company must meet at least two of these three criteria: Annual turnover of £1 million or less Balance sheet total of £500,000 or less 10 or fewer employees on average These thresholds took effect from 6 April 2025, increased from the previous limits (£632,000 turnover and £316,000 balance sheet), allowing more small businesses to benefit from simplified reporting. If your first accounting period is shorter than 12 months, the turnover threshold is reduced proportionately. The accounts you file must include a basic balance sheet showing your assets, liabilities, and equity. Unlike larger companies, you’re not required to file a profit and loss account publicly, though HMRC still needs one for your corporation tax return. Micro entity accounts are prepared under FRS 105, the accounting standard for micro entities. What Are the Most Common Accounting Errors? Small business owners make predictable mistakes when preparing micro entity accounts. These errors aren’t about being careless – they happen because the rules aren’t always clear, and many people are handling accounts for the first time. 1. Missing the Filing Deadline This is the single biggest mistake. You face three separate deadlines, each with its own penalty regime: Companies House accounts: 9 months after your financial year ends. File late and Companies House issues an automatic civil penalty: £150 if up to one month late, £375 for 1–3 months, £750 for 3–6 months, and £1,500 for more than 6 months. If you file late two years in a row, every penalty is doubled — a £150 penalty becomes £300. HMRC CT600 return: 12 months after your accounting period ends. From 1 April 2026, HMRC doubled the fixed late filing penalties for the first time since 1998: £200 for filing one day late, another £200 at three months, 10% of the unpaid tax at six months, and a further 10% at twelve months. File late three times in a row and the fixed penalties rise to £1,000 and £2,000. These apply even if you owe no tax. Corporation tax payment: 9 months and 1 day after your year-end — earlier than the CT600 deadline. Paying late triggers no fixed penalty, but HMRC charges interest daily from the day after the deadline. Since 6 April 2025 the rate is the Bank of England base rate plus 4% — currently 7.75% a year (base rate 3.75% from 9 January 2026). There is no grace period and no reasonable-excuse defence against interest. Many business owners confuse these deadlines or simply forget them. Penalties are automatic — there’s no warning letter and no second chance. The penalty applies even if you owe no tax. 2. Getting Your Company Classification Wrong Not every small company qualifies as a micro entity. If you’re a charity, a public company, or part of a group structure, you can’t use micro entity accounts even if you meet the size criteria. Filing the wrong type of accounts means Companies House will reject your submission, leaving you scrambling to redo everything before the deadline passes. Some companies also lose micro entity status mid-year because they grow beyond the thresholds. You must check your eligibility every year, not just once when you start. If you qualified last year but grew beyond the limits this year, you can still use micro entity accounts for one more year — after that, you’ll need to file small company accounts instead. 3. Recording Transactions Incorrectly This covers a wide range of problems: mixing personal and business expenses, recording VAT incorrectly, forgetting to log cash transactions, or categorising costs under the wrong headings. When your bookkeeping is messy, your accounts won’t balance. You’ll either pay too much tax or underpay and risk penalties later. A common example: putting a personal purchase through the business account and claiming it as a company expense. HMRC doesn’t allow this, and if caught during an investigation, you’ll owe back taxes plus interest. 4. Leaving Out Required Information Micro entity accounts still need specific details on your balance sheet: fixed assets, current assets, creditors, and share capital. Some business owners submit bare-minimum figures without proper breakdowns, thinking “simplified” means you can skip sections. It doesn’t. Incomplete accounts get rejected, and you’re back