From Companies House:
If you’re due to file accounts with Companies House by the end of September, use our online services where possible and allow plenty of time before your deadline.
It’s the directors’ responsibility to file a company’s accounts. You could get a criminal record, a fine or disqualification if you do not deliver your accounts on time.
File online before your deadline. We’ll send you an email to confirm we’ve received your accounts. We’ll send you another email when we’ve registered your accounts.
If you’re a small company, you cannot file abbreviated accounts anymore. Find out your accounts filing options for small companies.
You’ll still need to file accounts if your company is dormant.