The year-end change nobody diarised

The situation

Harbourline Logistics Ltd had always had a 31 December year end. Its practice, a five-person firm we will call Northbank Accounting, prepared the accounts each spring, and the deadline register said: accounts due 30 September, Corporation Tax due 1 October.

In January, Harbourline’s finance director decided to align the company’s year end with its new parent company and shortened the accounting period to 30 September using the Companies House online service. He mentioned it in an email to the bookkeeper, who was about to go on leave. The practice never saw it.

What went wrong

Shortening the period changed everything downstream:

• The company now had an accounting period ending 30 September of the previous year.
• Its accounts deadline was brought forward – to the later of 9 months after the new year end and 3 months from the date the change was filed.
• Its Corporation Tax payment for the shortened period was due 9 months and 1 day after the new period end.

The practice’s register still showed the old dates. Nobody noticed until the client forwarded a Companies House reminder that showed a deadline weeks earlier than expected.

What it cost

• The accounts were filed just in time after a scramble, but the Corporation Tax payment for the shortened period was made late, and HMRC charged late payment interest at the Bank of England base rate plus 4%.
• Staff time diverted from other clients in a busy month.
• A strained conversation with a director who believed he had told the practice.

How Deadlio would have caught it

1. The daily Companies House check. The day after the change was filed, the register would have shown a new “Next accounts made up to” date. Deadlio reads that date every day and would have moved the accounts deadline straight away.
2. The tax dates move with it. The Corporation Tax payment and CT600 dates are calculated from the next period end, so they would have updated too.
3. Warnings from the register itself. If Companies House shows a filing as overdue, or a company’s status changes, the client list flags it the next morning, so a problem that starts outside the practice is noticed rather than buried.
4. Overrides for the cases that matter. Where a practice makes the change itself, the Next period end – override field moves every related date at once and is cleared once filed.

Lessons for any practice

• Directors can change a year end in minutes online. Do not rely on being told.
• Check the Companies House register regularly, not just at year end.
• When a year end changes, review the Corporation Tax periods the same day.

Related guides

• Annual accounts filing deadline
• Corporation Tax payment deadline
• CT600 return filing deadline
• All deadline guides