For many limited companies across Wigan and the North West, September is not just the end of summer — it is one of the busiest compliance months of the year. Depending on your accounting reference date, 30 September 2026 can mean a Companies House filing deadline, a Corporation Tax return deadline, or the last chance to tidy the books before your own year-end closes.

None of this needs to be dramatic. Most penalties happen because directors leave the paperwork until the final week, not because the rules are unusually complicated. This guide sets out what falls due this month, what still needs doing if your year ends on 30 September, and a short checklist you can work through with your bookkeeper or accountant.

Companies House accounts: due if your year ended 31 December 2025

Private limited companies normally have nine months from the end of their accounting period to file annual accounts at Companies House. If your year ended on 31 December 2025, that deadline is 30 September 2026.

Late filing attracts an automatic civil penalty. For a private company the scale starts at £150 if you are up to one month late, rises to £375 for one to three months, £750 for three to six months, and £1,500 if you are more than six months late. File late two years running and the next penalty doubles. Companies House does not send a friendly reminder that resets the clock — once the date passes, the penalty applies.

If you are still chasing invoices, bank statements or stock figures for a December year-end, treat this week as the hard stop for gathering records. Our company accounts work covers statutory accounts preparation and filing for limited companies, and our company secretarial work sits alongside that for confirmation statements and Companies House housekeeping. Fee changes and register reform have also made timely filing more important.

Corporation Tax return: due if your year ended 30 September 2025

Your Company Tax Return (CT600) is separate from Companies House accounts. HMRC normally expects the return 12 months after the end of the accounting period. So if your company year ended on 30 September 2025, the CT600 is due by 30 September 2026.

Corporation Tax payment usually falls earlier — nine months and one day after the period end. For a 30 September 2025 year-end that payment date was 1 July 2026. If you have not yet paid, speak to HMRC or your accountant straight away; interest continues to run even when the return is still being finalised.

Do not assume that filing accounts at Companies House somehow covers HMRC. The two systems talk to each other in places, but you remain responsible for both. Practical help on rates, reliefs and returns sits on our Corporation Tax page.

If your year ends on 30 September 2026: use the next three weeks

Plenty of North West companies choose a September year-end. If that is you, the filing deadlines above are next year’s problem — but the tax planning window closes when the period ends. After 30 September you can still prepare accounts, yet you generally cannot move genuine trading decisions back into the closed year.

In the final weeks before year-end it is worth reviewing:

• Expected profit and cash — a rough full-year forecast stops you guessing when you look at bonuses, pensions or dividends.
• Director and staff expenses — mileage, subsistence and costs paid personally but not yet reimbursed often get missed until accounts season.
• Genuine bad debts — writing off a debt that is truly irrecoverable can only help if the paperwork and accounting treatment are correct before the year closes.
• Equipment and plant — if you were already planning to buy tools or machinery, bringing the purchase into use before year-end can affect capital allowances. Timing for its own sake is rarely wise; cash flow comes first.
• Employer pension contributions — contributions paid by the company before year-end are usually deductible in that period, subject to the normal “wholly and exclusively” rules.

For a clearer picture of what the company can and cannot claim, read what limited companies can and cannot claim as business expenses. If commercial property or fixtures are involved, ask us about capital allowances before you commit cash.

A practical September checklist for busy directors

You do not need a 40-page project plan. A short, honest pass through the following usually catches the problems that create late filings and unexpected tax bills:

1. Confirm your accounting reference date on Companies House and note the accounts, CT600 and Corporation Tax payment dates that follow from it.
2. Reconcile the business bank accounts and clear unmatched items in your bookkeeping software.
3. Chase overdue customer invoices and decide, with evidence, which debts are still collectable.
4. Pull together payroll summaries, VAT returns, CIS statements and any loan or director’s current account movements for the period.
5. List one-off items — new vehicles, major repairs, stock write-downs, grants — so nothing sits in a shoebox until January.
6. If you already run management accounts, produce a year-to-date pack now; it is far cheaper to fix issues before the year closes than after.

Cash still pays the wages and the tax. If September feels tight, look at debtor days and stock before you look at clever tax ideas. Steady cash control is covered in our wider cashflow guidance.

Who this matters to locally

We work with limited companies, sole traders and growing teams across Wigan, Standish, Appley Bridge and the wider North West. Whether you need a one-off year-end tidy-up or ongoing support, start with who we help and our full services overview.

If 30 September is on your calendar — for accounts, for a CT600, or because your own year-end is three weeks away — get the records in order now rather than on the afternoon of the deadline. Call 01257 255521, email [email protected], or use our contact page. We are at 39 Skull House Lane, Appley Bridge, Wigan WN6 9DR.