- Companies
- Civil engineering
- Holyhead
- Adeiladwyr Mon Cyf
Adeiladwyr Mon Cyf
- Company number
- 09915615
- Incorporated
- 14 Dec 201510 years trading
- Registered office
- Carreg Lwyd, Bryngwran, Holyhead, Anglesey, LL65 3RR
- Nature of business
- Construction of other civil engineering projects n.e.c.
Adeiladwyr Mon Cyf is a 10-year-old private limited company registered in Holyhead, company number 09915615, one of 6 civil engineering contractors in Holyhead. Its next accounts are due at Companies House on 31 December 2026, and the CT600 for the period to 31 March 2026 is due at HMRC on 31 March 2027.
Key dates
Worked out from the year end and filing history on the Companies House register.
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Finances
From each year's balance sheet filed at Companies House. Small companies do not have to publish turnover or profit, so these are balance sheet figures.
- Net assets down £33K (-44.3%) on the year before, to £42K.
- Net assets rose in 2 of 5 year-on-year comparisons on record.
- Current assets of £870K against £963K owed within a year: 0.9 times cover.
- 20 employees on average, down from 21 the year before.
- Balance sheets on record for 7 years, 2017 to 2025.
Net assets by year
| Year end | Net assets | Cash | Current assets | Owed within a year | Employees |
|---|---|---|---|---|---|
| 31 Mar 2025 | £42K | £1,513 | £870K | £963K | 20 |
| 31 Mar 2024 | £75K | £27K | £923K | £913K | 21 |
| 31 Mar 2023 | £47K | £17K | £780K | £769K | 23 |
| 31 Mar 2022 | £83K | £145K | £783K | £679K | 27 |
| 31 Mar 2021 | £67K | £194K | £523K | £509K | 26 |
| 31 Mar 2020 | £93K | £222K | £247K | £282K | 10 |
| 31 Mar 2017 | £832 | £37K | £78K | £87K | 17 |
Who runs and owns Adeiladwyr Mon Cyf
From the Companies House register. Individuals are shown by initials only; the full register is on Companies House.
Officers (2)
| Name | Role | Appointed |
|---|---|---|
| G*** W*** | Director | Aug 2019 |
| K*** D*** | Director | Apr 2022 |
3 former officers
| Name | Role | Appointed | Left |
|---|---|---|---|
| S*** W*** | Secretary | May 2018 | Aug 2019 |
| D*** A*** | Director | Dec 2015 | Aug 2017 |
| D*** O*** | Director | Dec 2015 | Feb 2022 |
Person with significant control
Where Adeiladwyr Mon Cyf is registered
The registered office is in Holyhead (LL65), in the Isle of Anglesey local authority area, Wales. Show LL65 3RR on a map.
Other trade companies in LL65
- Guy B Electrical LtdElectricians
- Ellis Property & Holdings LtdProperty developers
- Spotless Stay Cleaning LimitedCleaning companies
- Gwasanaethu Adeiladu Cyflawn CyfGroundworks and demolition
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- Arctic Blast Cleaning Solutions LtdCleaning companies
- Cybicleaningservices LtdCleaning companies
- Parkinson Plumbing and Heating LtdPlumbers and heating engineers
What happens if Adeiladwyr Mon Cyf files late
Companies House charges an automatic penalty the day after the deadline, and it rises the longer the accounts are late. These are the dates for this company's accounts due on 31 December 2026.
| Companies House | Accounts delivered | Penalty |
|---|---|---|
| Up to 1 month late | 1 Jan 2027 to 31 Jan 2027 | £150 |
| 1 to 3 months late | 1 Feb 2027 to 31 Mar 2027 | £375 |
| 3 to 6 months late | 1 Apr 2027 to 30 Jun 2027 | £750 |
| More than 6 months late | From 1 Jul 2027 | £1,500 |
Penalties double if the accounts were also late the year before.
| HMRC (CT600) | From | Penalty |
|---|---|---|
| 1 day late | 1 Apr 2027 | £200 |
| 3 months late | 30 Jun 2027 | another £200 |
| 6 months late | 30 Sep 2027 | HMRC estimates the tax and adds 10% of the unpaid tax |
| 12 months late | 31 Mar 2028 | another 10% of any unpaid tax |
For returns filed on or after 1 April 2026. Late three times in a row and the £200 penalties become £1,000 each.
Company details
As held on the Companies House register.
- Company number
- 09915615
- Status
- Active
- Company type
- Private limited company
- Incorporated
- 14 December 2015 (10 years ago)
- Registered office
- Carreg Lwyd, Bryngwran, Holyhead, Anglesey, LL65 3RR
- Nature of business
- Construction of other civil engineering projects n.e.c. (SIC 42990)
- Year end
- 31 March (accounting reference date)
- Accounts type
- Unaudited abridged
- Last accounts made up to
- 31 March 2025
- Last confirmation statement
- 31 March 2026
- Previous names
- Adeiladwr Mon Cyf (until 14 Apr 2016)
Filing notes for civil engineering contractors
Civil engineering contractors usually carry plant and machinery, so capital allowances (the annual investment allowance and the main pool) do much of the work in the corporation tax computation.
Similar companies in Holyhead
Other active civil engineering contractors registered in Holyhead.
- Awh Plant Limited2024
- Gardner Powerline Maintenance Limited2022
- Mon Civils Limited2023
- NJM Engineering Surveyors Ltd2025
- True North Surveying Ltd2022
All civil engineering contractors in Holyhead · All trades in Holyhead · Civil engineering across the UK
Frequently asked questions
When are Adeiladwyr Mon Cyf's accounts due?
Adeiladwyr Mon Cyf's next accounts are due at Companies House by 31 December 2026 (in 79 days), covering the period to 31 March 2026.
When is Adeiladwyr Mon Cyf's CT600 due?
The CT600 for the period to 31 March 2026 is due at HMRC by 31 March 2027, 12 months after the period end. The corporation tax itself is payable earlier, by 1 January 2027.
Is Adeiladwyr Mon Cyf still trading?
Adeiladwyr Mon Cyf is listed as active on the Companies House register as of 1 Oct 2026. Active means it has not been dissolved or entered insolvency; it does not show whether it is currently taking on work.
What does Adeiladwyr Mon Cyf do?
Adeiladwyr Mon Cyf is registered under Construction of other civil engineering projects n.e.c. (SIC 42990).
How old is Adeiladwyr Mon Cyf?
Adeiladwyr Mon Cyf was incorporated on 14 December 2015, 10 years ago.
Who runs Adeiladwyr Mon Cyf?
Adeiladwyr Mon Cyf has 2 active directors, the longest-serving appointed in Aug 2019. Their names and service addresses are on the Companies House register.
Who owns Adeiladwyr Mon Cyf?
One person or company has significant control of Adeiladwyr Mon Cyf: an individual (owns 75% or more of the shares).
What is the penalty if Adeiladwyr Mon Cyf files its accounts late?
Companies House charges £150 if the accounts are up to 1 month late, £375 up to 3 months, £750 up to 6 months and £1,500 after that, doubled if the previous year's accounts were also late. HMRC charges £200 for a CT600 filed a day late and another £200 at 3 months.
Official records
View Adeiladwyr Mon Cyf on Companies House for filed documents, officers and the full history.
Based on the Companies House register (snapshot 1 Oct 2026). Deadlines are worked out from the register and assume a standard accounting period; a change of year end or a short period moves them. This page is general information, not tax or accountancy advice.