- Companies
- Plumbers and heating engineers
- London
- S I Mechanical-Installation Ltd
S I Mechanical-Installation Ltd
- Company number
- 10553909
- Incorporated
- 9 Jan 20179 years trading
- Registered office
- 129 Colney Hatch Lane, London, N10 1HD
- Nature of business
- Plumbing, heat and air-conditioning installation
S I Mechanical-Installation Ltd is a 9-year-old private limited company registered in London, company number 10553909, one of 2,972 plumbing and heating companies in London. Its next accounts are due at Companies House on 31 December 2026, and its first CT600 is due at HMRC on 31 January 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 up £128K (+41.7%) on the year before, to £434K.
- Net assets rose in 6 of 7 year-on-year comparisons on record.
- Current assets of £479K against £74K owed within a year: 6.5 times cover.
- 4 employees on average, up from 3 the year before.
- Balance sheets on record for 8 years, 2018 to 2025.
Net assets by year
| Year end | Net assets | Cash | Current assets | Owed within a year | Employees |
|---|---|---|---|---|---|
| 31 Jan 2025 | £434K | £263K | £479K | £74K | 4 |
| 31 Jan 2024 | £306K | £139K | £323K | £34K | 3 |
| 31 Jan 2023 | £275K | £311K | £56K | 2 | |
| 31 Jan 2022 | £112K | £132K | £21K | 2 | |
| 31 Jan 2021 | £92K | £214K | £74K | 2 | |
| 31 Jan 2020 | £56K | £74K | £22K | 2 | |
| 31 Jan 2019 | £63K | £129K | £70K | 2 | |
| 31 Jan 2018 | £343 | £59K | £64K | 2 |
Where S I Mechanical-Installation Ltd is registered
The registered office is in London (N10), in the Barnet local authority area, London. Show N10 1HD on a map.
Other trade companies in N10
- Endo Climates LimitedPlumbers and heating engineers
- Bjpwaterworks LtdProperty developers
- Oxman LimitedProperty developers
- Union Traffic Management LtdLandscapers and gardeners
- National Engine Solutions LimitedMotor traders
- A&D Building Solutions LtdProperty developers
- Primeropesolutions LtdSpecialist contractors
- The Aircon Market LtdPlumbers and heating engineers
Also registered at this address
9 other companies use the same registered office as S I Mechanical-Installation Ltd.
- Alanandjo LtdBuilders
- Cos Gas Plumbing & Heating LimitedPlumbers and heating engineers
- Dewolf Design and Build LtdProperty developers
- G.A.G LimitedLandscapers and gardeners
- Hastings & Jones LtdProperty developers
- Modern Joinery and Construction LtdProperty developers
- Monte Design LtdProperty developers
- Narta LtdProperty developers
- The Greek Gardener LtdLandscapers and gardeners
What happens if S I Mechanical-Installation Ltd 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
- 10553909
- Status
- Active
- Company type
- Private limited company
- Incorporated
- 9 January 2017 (9 years ago)
- Registered office
- 129 Colney Hatch Lane, London, N10 1HD
- Nature of business
- Plumbing, heat and air-conditioning installation (SIC 43220)
- Year end
- 31 March (accounting reference date)
- Accounts type
- Total exemption (full)
- Last accounts made up to
- 31 January 2025
- Last confirmation statement
- 23 December 2025
Filing notes for plumbing and heating companies
Plumbing and heating companies frequently work under CIS for main contractors and also directly for homeowners, so turnover can mix CIS and non-CIS income.
Similar companies in London
Other active plumbing and heating companies registered in London.
- S Marson Plumbing Ltd2015
- S R Gas Consultancy Services Limited2015
- S&C Heating Services Ltd2017
- S&G Heating Solutions Ltd2020
- S&J Advisors Limited2026
- S&L Cooling and Heating Ltd2026
- S&M Property Services Ltd2025
- S&M Top Ltd2015
All plumbing and heating companies in London · All trades in London · Plumbers and heating engineers across the UK
Frequently asked questions
When are S I Mechanical-Installation Ltd's accounts due?
S I Mechanical-Installation Ltd's next accounts are due at Companies House by 31 December 2026 (in 79 days), covering the period to 31 March 2026.
When is S I Mechanical-Installation Ltd's CT600 due?
The first accounts cover more than 12 months, so there are two Company Tax Returns: one for the 12 months to 31 January 2026, due by 31 January 2027, and one for the period to 31 March 2026, due by 31 March 2027. Corporation tax is payable 9 months and 1 day after the end of each.
Is S I Mechanical-Installation Ltd still trading?
S I Mechanical-Installation Ltd 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 S I Mechanical-Installation Ltd do?
S I Mechanical-Installation Ltd is registered under Plumbing, heat and air-conditioning installation (SIC 43220).
How old is S I Mechanical-Installation Ltd?
S I Mechanical-Installation Ltd was incorporated on 9 January 2017, 9 years ago.
What is the penalty if S I Mechanical-Installation Ltd 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 S I Mechanical-Installation Ltd 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.