Filing your small UK startup’s annual accounts: a practical guide

understanding your filing obligations

Every limited company in the UK must file annual accounts, even if it’s dormant or early-stage. For a small startup with no in-house finance team, the process can feel daunting. Getting it right keeps your company in good standing with Companies House and HMRC, and avoids late filing penalties that can add up fast.

This guide walks through the essentials for micro-entities and small companies. It’s not legal or tax advice. If you’re unsure about your numbers, speak to an accountant.

what counts as a small company or micro-entity

Your filing options depend on your company’s size. For accounting periods starting on or after 1 January 2016, you can qualify as a micro-entity if you meet at least two of these thresholds:

• turnover of £632,000 or less
• balance sheet total of £316,000 or less
• 10 employees or fewer

A small company must meet at least two of:

• turnover of £10.2 million or less
• balance sheet total of £5.1 million or less
• 50 employees or fewer

Most early-stage startups will fall under the micro-entity regime, which allows simpler, less detailed accounts.

what you need to file

for companies house

You must file a set of statutory accounts. For a micro-entity, this can be a simplified balance sheet and a few notes, plus a directors’ report if you choose to prepare one. No profit and loss account is required at Companies House. A small company files an abridged balance sheet, an abridged profit and loss account, and a directors’ report. Both regimes allow you to send only the minimum required publicly.

Even if the company is dormant, you still need to file dormant accounts. This is a simple balance sheet showing no significant transactions.

for hmrc

You must also file a company tax return (CT600) and include full accounts: profit and loss, balance sheet, and any notes needed to support your corporation tax calculation. HMRC gets the full picture, not just the abridged version. You’ll also need to calculate your corporation tax liability and pay it by the deadline.

key deadlines

The first set of accounts is due 21 months after the date you incorporated. For subsequent years, you have 9 months from your accounting reference date (ARD) to file with Companies House. The ARD is usually the end of the month you incorporated. You can change it, but be careful: shortening the period can bring the deadline forward.

The company tax return and any corporation tax payment are due 12 months after the end of your accounting period. However, HMRC’s filing deadline is often earlier than the payment deadline: you must file the return within 12 months, but payment is due 9 months and 1 day after the period end. For many small companies, both deadlines are effectively the same 9-month window for filing with Companies House, so plan to do both together.

Late filing at Companies House triggers automatic penalties:

• 1 day late: £150
• 1 month late: £375
• 3 months late: £750
• 6 months late: £1,500

HMRC penalties for late filing of the tax return start at £100 and increase over time. Interest on late tax payments accrues daily.

preparing your accounts

Most founders don’t prepare accounts from scratch. You’ll likely use accounting software or a bookkeeper who produces a trial balance and draft accounts. You then need to decide if you’re filing as micro-entity or small company. The micro-entity route is less work: you only need to extract the balance sheet figures and a few notes. You can use the Companies House online service or compatible software to file.

If you’re using an accountant, they will typically prepare the accounts and file them for you. But you remain legally responsible, so you should review the documents before they’re submitted.

how to file

You can file accounts online with Companies House using the WebFiling service or third-party software. The balance sheet and notes are entered into a web form. You’ll need your company authentication code. For the tax return, HMRC accepts filing through commercial software or its own online service. Many accounting platforms can handle both filings in one go.

Make sure you file the same set of accounts to Companies House and HMRC at the same time. The figures that underpin both submissions must be consistent. If you prepare full accounts internally, you’ll send the abridged version to Companies House and the full version to HMRC.

common mistakes to avoid

• missing the first deadline: new directors often assume they have 21 months, but that’s only for the first period. The second year’s deadline can sneak up.
• filing dormant accounts for a company that made a single transaction: even a small bank charge can break dormancy. If in doubt, file full accounts.
• forgetting to include directors’ loans or inter-company balances: these must be disclosed in the notes.
• leaving the registered office address unconfirmed: make sure your Companies House records are up to date; otherwise you might miss penalty notices.

keeping things organised

Store your filed accounts and the underlying records for at least six years. Keep your accounting reference date, company authentication code, and HMRC credentials in a secure place. If you use StartupDocs, you can store the final PDFs alongside your other compliance documents so everything is in one place.

Filing annual accounts is a chore, but it’s a predictable one. Once you know the rules and deadlines, it becomes a routine task you can handle with a good process and a little help from your accountant.