Legal Diary: Monthly and Annual Tax Deadlines

Tax deadlines aren’t just dates on a calendar – they’re make-or-break moments for cash flow, compliance, and peace of mind. Miss one, and you risk penalties, interest, or even HMRC scrutiny. This detailed guide arms UK small business owners with a comprehensive, month-by-month and annual diary of every key tax and legal deadline you need to know. From PAYE and VAT to Companies House filings, we cover what’s due, when, and what happens if you slip up – so you can plan ahead and avoid nasty surprises.

Deadlines are the backbone of business compliance in the UK. Missing a tax or legal deadline doesn’t just result in a slap on the wrist – it can trigger automatic penalties, interest charges, and even in some cases, legal action. For small businesses, where cash flow is often tight and staffing limited, a missed deadline can quickly spiral into bigger financial and reputational problems. HMRC’s systems are increasingly automated, meaning late filings or payments are picked up immediately.

On top of fines, late submissions can raise red flags with HMRC or Companies House, increasing the risk of audits or investigations. This can mean more paperwork, more stress, and potential disruption to your business operations. It’s also worth remembering that some filings, like VAT returns or payroll submissions, are directly linked to your ability to trade or pay staff on time. Staying on top of your legal diary isn’t just about ticking boxes – it’s about protecting your business.

Many business owners underestimate just how many deadlines there are, especially if you’re juggling VAT, payroll, corporation tax, and company filings. Add in changing tax rules, public holidays, and sector-specific requirements, and it’s no wonder things get missed. That’s why a clear, up-to-date legal diary is an absolute must – not just for your accountant, but for you as a business owner.

Every month brings its own set of recurring deadlines for UK small businesses. The most common are PAYE (Pay As You Earn) for payroll, VAT returns (if you’re VAT registered), CIS (if you work in construction), and pension auto-enrolment duties. Understanding not just the dates, but the specific actions required, is critical. For example, submitting a payroll RTI (Real Time Information) report to HMRC isn’t the same as paying the tax due – both have their own deadlines.

PAYE payments and submissions are due each month for any business with employees, even if you only pay yourself as a director. VAT deadlines depend on your VAT quarters, but most small businesses operate on a quarterly or monthly basis. If you’re in the Construction Industry Scheme (CIS), monthly returns and payments are mandatory if you’re a contractor. Pension contributions must be paid by the 22nd of each month if you pay electronically, or the 19th if by post.

Missing these monthly obligations can result in instant penalties. For example, late PAYE submissions incur an automatic fine after one late filing in a tax year, and repeated lateness ramps up the penalties. VAT penalties depend on your turnover and how late you file. Keeping a recurring, month-by-month checklist is your best defence.

• PAYE submissions must be made each pay period, not just monthly, if you pay weekly or irregularly.
• VAT deadlines are specific to your assigned VAT quarters, but monthly VAT is common for higher turnover or repayment businesses.
• CIS returns are due even if you made no payments to subcontractors that month – you must submit a 'nil' return.
• Pension duties are ongoing: you must pay contributions and complete any required re-enrolment or re-declaration tasks on time.

Annual deadlines are the big ones – miss them, and you’re likely to face immediate, significant penalties. The most critical are the Self Assessment tax return (for sole traders, partnerships, and directors), Corporation Tax return (CT600), annual accounts to Companies House, and annual confirmation statement. Each has its own timeframes and quirks.

Self Assessment tax returns are due by 31 January for online filings, covering the previous tax year (which runs 6 April to 5 April). If you file on paper, the deadline is earlier (31 October). Corporation Tax returns are due 12 months after your company’s accounting period ends, but any tax due must be paid within 9 months and 1 day of your year-end – a common source of confusion. Companies House annual accounts are usually due 9 months after your company’s financial year-end, while the confirmation statement is an annual update of your company’s key details, due every 12 months.

Missing annual deadlines is costly. For example, Companies House will automatically fine you £150 if your accounts are late by even one day, increasing to £1,500 after 6 months. HMRC late filing penalties for Self Assessment start at £100 and escalate if you delay further. These deadlines are not negotiable, so diarising them is essential.

• If your accounting period changes, Companies House and HMRC deadlines may shift – always confirm your new due dates.
• You must file a confirmation statement even if nothing has changed in your company details.
• Dormant companies still need to file annual accounts and a confirmation statement.
• Self Assessment late payment interest is currently 7.75% (as of June 2026) – higher than many business loans.

VAT is one of the most common – and confusing – sets of deadlines for UK small businesses. Most VAT-registered businesses operate on quarterly periods, but some are monthly (usually if you’re regularly in repayment), and a few use the annual accounting scheme. Your VAT return and payment are usually due one calendar month and seven days after the end of your VAT period. For example, if your quarter ends 31 March, your return and payment are due by 7 May.

It’s vital to know your VAT stagger – your specific quarters assigned when you registered for VAT. These won’t necessarily line up with the tax year or your company year-end. You can view your VAT periods in your HMRC Business Tax Account. Deadlines falling on weekends or bank holidays are not extended – you must file and pay by the last working day before the deadline. Penalties for late submission, late payment, or errors can be severe, especially now that HMRC’s penalty regime for VAT was overhauled in 2023.

For those using the annual accounting scheme, you make advance payments throughout the year, with a final balancing payment and return due two months after the end of your VAT year. Always check your scheme requirements, as deadlines and obligations differ. If you’re using Making Tax Digital (MTD) for VAT, you must file returns using compatible software – spreadsheets and paper are no longer acceptable for most businesses.

• Check your VAT stagger dates in your HMRC account – don’t assume your quarters are Jan-Mar, Apr-Jun, etc.
• Allow at least 3 working days for BACS payments to reach HMRC if paying close to the deadline.
• Switching VAT schemes (e.g., from quarterly to annual) will change your deadlines – get written confirmation from HMRC.
• Always file a ‘nil’ VAT return if you have nothing to declare – missing the deadline still triggers penalties.

Running payroll in the UK means monthly (or more frequent) reporting to HMRC, as well as annual end-of-year filings. Every time you pay staff, you must submit a Full Payment Submission (FPS) to HMRC on or before payday. If you make any adjustments (starters, leavers, corrections), you may also need to submit an Employer Payment Summary (EPS). PAYE and NICs must be paid to HMRC by the 22nd of the following month if paying electronically, or by the 19th if paying by post.

At the end of each tax year (5 April), employers must complete year-end tasks, including issuing P60s to employees by 31 May, and submitting the final payroll report. If you provide benefits or expenses to staff, you also have to deal with P11D and P11D(b) forms by 6 July, and pay any Class 1A NIC due by 22 July. These deadlines are strict, and missing them carries automatic penalties per employee or form.

Small businesses often trip up on ‘occasional payroll’ – even if you only pay yourself as a director once per year, you still need to file an FPS for that pay date. If you don’t pay anyone in a tax month, you must submit an EPS to tell HMRC no payment was made. RTI (Real Time Information) compliance is now mandatory for all UK employers, regardless of size.

• Always check HMRC’s online portal after submitting FPS/EPS to confirm receipt.
• Late P60s or P11Ds carry per-employee fines – don’t wait until the last minute.
• P11Ds are needed even for directors if you’ve claimed company expenses or benefits.
• If you cease employing staff, you must submit a final FPS and inform HMRC the scheme is closed.

All limited companies and LLPs must file annual accounts and a confirmation statement to Companies House. The deadlines are fixed by your company’s accounting reference date (ARD), which is normally the last day of the month you incorporated. Accounts are due 9 months after your year-end, and the confirmation statement must be filed at least once every 12 months – you choose the review period, but it’s often easiest to align with your accounts or tax deadlines.

If you miss the accounts deadline, Companies House automatically issues a late filing penalty, starting at £150 and rising to £1,500 if over 6 months late. Repeated lateness doubles the penalty. The confirmation statement (previously the annual return) carries its own £150 penalty if missed, and persistent failure can lead to your company being struck off the register. Even dormant or non-trading companies must file both documents.

Certain changes – like appointing new directors, changing your registered office, or updating shareholder details – must be reported to Companies House as soon as possible, not just at the annual statement. Failing to keep your company details up to date can have serious consequences, including legal action against directors. Always use the Companies House WebFiling service or approved software, and check for confirmation of submission.

• You can file dormant accounts if your company hasn’t traded – but you must still file on time.
• Use Companies House email reminders – they’re free and provide a useful backup to your own diary.
• If you change your company year-end, check new deadlines carefully – they may shift from your original dates.
• Directors are personally liable for missed filings, not just the company itself.

Some deadlines are unique to particular industries or types of business. For example, if you operate in construction, the Construction Industry Scheme (CIS) imposes monthly returns and payment deadlines. Charities have specific filing and reporting dates with the Charity Commission, and businesses regulated by the FCA or other authorities may have their own statutory returns. If you sell alcohol or tobacco, you’ll have licensing or duty returns. Don’t assume all deadlines are HMRC or Companies House – you may need to keep a separate diary for sector regulators.

CIS contractors must file a monthly return by the 19th following the end of the tax month. Late returns trigger instant £100 penalties, with further fines as lateness continues. Charities must file an annual return with the Charity Commission within 10 months of their financial year-end (if income is over £10,000), plus annual accounts. FCA-regulated firms have their own regime of reporting deadlines, which can be quarterly, half-yearly, or annual depending on your authorisation.

The Information Commissioner’s Office (ICO) requires annual data protection fee renewals for most businesses processing personal data. Health and Safety Executive (HSE) reports, such as RIDDOR incident reports, have their own strict deadlines, often within days of an incident. Always check with your professional body or sector regulator for calendar requirements beyond tax and company law.

• Double-check any sector-specific calendars published by your regulator or trade body.
• CIS returns are required even if no subcontractors were paid – submit a ‘nil’ return.
• Data protection fee renewal is often overlooked – set an annual reminder in your diary.
• Reporting serious workplace incidents to HSE must be done within 10 days (or immediately in some cases).

A good legal diary is your best insurance policy against missed deadlines. Start by mapping out every recurring and one-off deadline that applies to your business – monthly, quarterly, and annual. Include tax returns, payments, Companies House filings, payroll duties, pension contributions, and any sector-specific requirements. Don’t just rely on your accountant; as a director or proprietor, you are personally responsible for compliance.

The most effective approach is to use a dual system: a digital calendar (such as Google Calendar or Outlook) with automated reminders set for key dates, plus a physical wall planner or spreadsheet visible in your office. Colour-code deadlines by type (e.g., red for tax, blue for payroll) and include both filing and payment due dates. Share the calendar with any staff or advisers responsible for compliance, so nothing gets missed if someone is off sick or leaves the business.

Regularly review and update your diary whenever your circumstances change – new staff, change of VAT scheme, updated company year-end, or new regulatory obligations. Build in reminders at least two weeks before each deadline to allow for gathering paperwork, system glitches, or payment delays. If you use accounting software, check if it offers integrated compliance calendars and alerts.

• Leverage HMRC and Companies House email reminders – sign up for every available alert.
• Keep copies of all submissions and payment confirmations – don’t assume digital filings always go through.
• Allocate time in your diary each month to review upcoming deadlines and chase any missing paperwork.
• Treat compliance as a core part of your business operations, not an afterthought.

The most frequent cause of missed deadlines is assuming someone else is handling it – especially if you work with an external accountant or bookkeeper. Remember, HMRC and Companies House hold directors and business owners ultimately responsible, whatever your internal arrangements. Another common mistake is confusing submission and payment deadlines – they’re often separate, and both must be met.

Many small businesses also underestimate the impact of public holidays, IT failures, or staff absences. If a deadline falls during a holiday or you’re away, you’re still liable. HMRC rarely offers leeway unless you can prove a genuine, unavoidable problem (such as a national outage or bereavement). Always build in a buffer and have a backup person able to submit filings or make payments on your behalf.

Penalties for late filings escalate quickly. For example, Self Assessment starts with a £100 fine but adds daily penalties after 3 months. VAT late submission penalties (since 2023) are now points-based, and repeated lateness can mean thousands in fines. Companies House doubles your late filing penalty if you’re late two years in a row. The reputational impact can be just as damaging – especially if you’re seeking finance, tenders, or partnerships.

• Never ignore penalty notices – respond immediately and appeal if you have a valid reason.
• Don’t rely solely on your accountant. You must check that filings have actually been made.
• Keep written evidence of any technical issues, correspondence, or appeals to support your case if you’re late.
• If you genuinely can’t meet a deadline, contact HMRC or Companies House in advance – they may offer a short extension for serious reasons.