UK Limited Company Accounting 101: A Beginner’s Guide to Your First Year (Deadlines, Records, VAT)

Understand Your First Accounting Period (It Sets Every Deadline)

Your first accounting period starts on your incorporation date and usually ends on the last day of the same month the following year. This often makes your first period slightly longer than 12 months. That date then drives your statutory accounts deadline and your corporation tax timeline.

For example, if you incorporated on 15 May 2025, your accounting reference date would be 31 May 2026. Set this date in your calendar now. Everything else follows from it.

Mark These Deadlines (Penalties Are Automatic)

Missing deadlines triggers automatic fines from Companies House and HMRC. They escalate. Protect your cash flow by treating these as non-negotiable:

1. File Statutory Accounts (Companies House): In your first year, you must file within 21 months of incorporation. After that, it’s 9 months after your year end.
2. Pay Corporation Tax (HMRC): You must pay Corporation Tax 9 months and 1 day after your accounting period ends. Payment is due even if your final accounts filing is still in progress.
3. File Your Company Tax Return (CT600): You must file within 12 months of your accounting year end.

Do this monthly: update bookkeeping, reconcile the bank, and review taxes. This prevents last-minute errors and helps you file on time, every time.

Keep These Records for 6 Years (HMRC Will Expect Proof)

HMRC requires you to keep business records for at least 6 years. If HMRC asks, you must be able to evidence income, costs, and taxes with clear documentation. No gaps. No “best guesses”.

Keep these records consistently:

• Sales evidence: invoices and platform reports for Shopify, Amazon, and B2B sales.
• Purchase receipts and bills: including software, advertising, subscriptions, freight, and professional fees.
• Bank statements and card statements: always use a dedicated business account to keep transactions clean.
• Payroll records: payslips, RTI submissions, and director salary documentation where applicable.

This is where structured systems pay off. With a tech-driven accounting setup, you capture transactions monthly, attach source documents, and keep a complete audit trail—so your year-end is fast, accurate, and far less stressful.

VAT: Register on Time (Or You Create Backdated Risk)

VAT is one of the fastest ways a growing business becomes unintentionally non-compliant. If your taxable turnover exceeds £90,000 in any rolling 12-month period, you must register for VAT. This is not optional. Late registration can mean backdated VAT bills, penalties, and hours of clean-up.

Many businesses also choose voluntary VAT registration before the threshold. The benefits are straightforward:

• Reclaim VAT: claim back VAT on eligible business purchases.
• Look established: helpful for B2B credibility and supply chain conversations.
• Scale smoothly: you implement the right process before growth forces it.

With a structured VAT workflow, you track the rolling threshold monthly and prepare returns with clean reconciliations—so VAT doesn’t become a surprise problem.

Why Cross-Border Experience Matters in Your First Year

If you sell internationally or plan to, you need a system built for cross-border trading from day one. This includes:

• Cross-border VAT: EU selling can trigger OSS/IOSS considerations. Getting it wrong can delay goods at customs and create unexpected VAT liabilities.
• Multi-currency bookkeeping: USD/EUR/GBP must be reconciled properly so your reports reflect real margins, not distorted FX noise.
• International compliance: spot where you may create additional tax obligations, so you avoid duplicate reporting and expensive fixes.

A structured system now prevents painful rework later. Building clean accounts that scale with you from inception is far more cost-effective than fixing them after problems arise.

Your First Year Checklist: A Step-by-Step Guide

To ensure a smooth first year, follow this simple checklist:

1. Appoint a Professional: Don’t DIY your accounts. A qualified accountant will likely save you more in tax than they cost in fees.
2. Set Up Cloud Accounting: Connect your bank feeds and sales channels (Amazon, eBay, Shopify) immediately.
3. Review VAT Monthly: Track your rolling 12-month turnover. Don’t wait for the end of the year to see if you’ve crossed the £90,000 limit.
4. Set Aside Tax Money: As a rule of thumb, move 20-25% of your profit into a separate savings account so you aren’t caught short when the Corporation Tax bill arrives.
5. Plan for International Growth: Even if you only sell in the UK now, structure your accounts to handle cross-border transactions later.

Frequently Asked Questions for New Ltd Company Owners

When is my first set of accounts due at Companies House?

Your first statutory accounts are due 21 months after incorporation. After the first year, accounts are due 9 months after your company year end. Missing this deadline triggers automatic penalties.

When do I have to pay Corporation Tax?

You must pay Corporation Tax 9 months and 1 day after your accounting period ends. Pay on time to avoid interest and late payment consequences.

When is my Company Tax Return (CT600) due?

Your CT600 must be filed within 12 months of your accounting period end. Filing late can trigger HMRC penalties.

How long do I need to keep accounting records?

You must keep business records for at least 6 years. This includes sales invoices, purchase receipts, bank statements, and payroll documentation. HMRC can request these records at any time to verify compliance.

What happens if I miss a deadline?

Missing deadlines triggers automatic penalties from both Companies House and HMRC. Penalties escalate with repeated breaches. Penalties for late accounts filing start at £150 (if up to 3 months late) and increase significantly for longer delays. Late Corporation Tax payment incurs interest and potential penalties of up to 5% of the tax due.

Do I need to register for VAT immediately?

You must register for VAT once your taxable turnover exceeds £90,000 in any rolling 12-month period. You can also register voluntarily before this threshold. Monitor your turnover monthly to ensure you register on time and avoid backdated VAT liabilities.