Companies House filings look simple from the outside. Inside a busy practice, they are the source of more avoidable losses than almost any other recurring task: missed deadlines, penalty doublings, register rejections, and the time spent unwinding errors that should never have been made. This list is the ten that come up most often, ranked by how much they actually cost when they happen.
1. Filing the CS01 on the 14-day deadline rather than inside the 60-day window
Treating the 14-day grace as the deadline removes all margin for error. A bank-holiday weekend, a sick employee, or a payment-card failure on the day of filing turns into a late submission and a strike-off notice three months later. File inside the 60-day early window as a matter of policy. The system permits it, the next confirmation date adjusts to a year from the date filed, and you remove the cliff-edge risk entirely.
2. Forgetting that the previous year was late (the doubling rule)
A £1,500 penalty becomes £3,000 the second year running. Firms that do not maintain a doubled-risk register lose tens of thousands of pounds in client penalties (and sometimes write them off as goodwill). Tag every client whose previous accounts were filed late and treat their next ARD as untouchable.
3. Filing PSC02 instead of looking through to a UBO
When a corporate shareholder is offshore and not subject to equivalent disclosure, PSC02 is wrong. You look through to the individual ultimate beneficial owner and file PSC01. Getting this wrong on a complex group structure leaves the register technically inaccurate, which becomes an ECCTA enforcement risk and can complicate AML supervision visits.
4. Updating the PSC on the CS01 instead of filing the underlying PSC form
The CS01 confirms the existing register state. It does not change it. A new PSC must be filed on PSC01 within 14 days of the company becoming aware of the change. Trying to introduce a new PSC via the CS01 alone leaves a gap in the change history that surfaces in due diligence and at refinancing.
5. Using the registered office for client mail without an SLA
Many firms offer a registered-office service as an add-on but do not commit to a defined turnaround for incoming statutory mail. Under the formal-communications regime, a 10-day delay between Companies House posting and the client seeing the letter can mean a missed direction-notice deadline. Set an SLA (48 hours is standard), document it, and resource it.
6. Not updating the SIC code after a real change in trade
SIC codes are confirmed on every CS01 and are the basis for some HMRC risk assessments and lender underwriting. A company that pivoted from retail to wholesale and never updated the SIC is creating its own risk-rating noise. The SIC code is updated through the CS01 or on a standalone basis if the change matters before the next confirmation date.
7. Filing accounts on the wrong template after a company-size change
Crossing the small-company threshold (or losing the right to file abridged accounts) and continuing to file under the old regime is rejected by Companies House and can trigger formal queries under ECCTA. Recheck the size category at each year-end, not just at incorporation.
8. Submitting amended accounts to fix something that does not actually need amending
Amended accounts are a formal, public correction and stay on the register permanently as an amendment. For minor disclosures, it is often better to address the issue in the following year's comparatives rather than amending. The cost of an unnecessary amendment is reputational, not financial - but it shows up in every credit search forever.
9. Treating a director resignation as a same-day administrative task
A director resignation requires TM01 filed within 14 days. Where the resigning director was also the registered email address contact or the registered office occupier, the company can lose its ability to receive Companies House correspondence between resignation and the filing of replacement details. Sequence the changes in the right order.
10. Relying on memory or a single spreadsheet for the firm-wide deadline register
Spreadsheets do not raise alarms. They do not surface red-amber-green status, do not assign owners, and do not survive staff turnover. A 200-client firm running its Companies House deadlines from a partner's Excel file is one resignation away from a year of penalties. Accupe's Compliance Radar pulls the ARD, confirmation date and PSC status for every client from the Companies House sync and surfaces them on Smart Boards by owner and by week. The firm files via its usual software - Accupe does not submit to Companies House - but the deadlines, ownership and escalation are all in one place.
Closing
Most of these mistakes are made by good firms with good intentions and a busy quarter. None of them are intellectually hard to avoid. They become routine when the firm has a deadline workflow that surfaces the right work to the right person at the right time, and a culture that treats Companies House filings as work-in-progress until the confirmation lands - not until the form is sent.