Day nineteen
The scaffold came down a fortnight ago. The customer has paid. The van is two jobs away. And the certificate has not been created, because the commissioning readings are on a phone that has since been through a wash cycle, and the person who supervised the job was a subcontractor whose surname you have never once needed until this morning.
Nobody plans this. The certificate is treated as office work, the office work happens after the site work, and by the time anyone opens the file the site is gone.
"On smaller installations, I get the feeling a similar amount of time will be spent in the office complying with MCS guff than will be spent on site."
— an installer on ElectriciansForums, July 2021
Nearly five years old, and it has aged well.
What the reminder says
On 14 May 2026 MCS published a compliance reminder. The wording is short:
"an MCS certificate must be created no later than 14 days after a system's commissioning date"
and
"MCS is consistently monitoring the Scheme to ensure compliance with this requirement."
This is not a new rule. It is a reminder of an existing one, which tells you something on its own. Nobody reminds people about a requirement everybody is already meeting.
MCS also notes that late certificates "may cause delays in the grant being paid." That is the entirety of the published consequence. Be exact about it, because the version that reaches you third-hand in a WhatsApp group will be worse.
Fourteen days is generous
Fourteen days is a long time. If the commissioning data is captured at commissioning — on the day, on the roof, into something that is not a person's memory — creating the certificate is a short job you do on the Monday.
Fourteen days is also no time at all. If the certificate has to be reconstructed from a phone, a van and a WhatsApp thread, day 14 arrives while you are still working out which Thursday the system was commissioned on.
The difference between those two firms is not discipline. It is where the data lives.
MCS reports 267,032 solar PV installations in 2025. That is 267,032 fourteen-day clocks, each started on a roof and stopped in an office. The clock is not the problem. The handoff leaks.
| The fact | Where it lives at 4pm on commissioning day | Where it lives on day 14 |
|---|---|---|
| The commissioning date — the clock starts here | On a form, or in someone's head | "It was a Thursday. Possibly the Thursday before." |
| The full name of the person who supervised the install | On site, in a van | A phone contact saved as a first name and a trade |
| What was actually fitted, versus what was designed | Marked up on the layout, or not marked up at all | A disagreement with the surveyor |
| The customer's copy of everything | Promised | Requested. Then requested again. |
The name that is in nobody's system
The redeveloped Installer Scheme is rolling out, per the IAA, "throughout 2026 and into 2027". In MCS's guidance on the new business roles, one line does more work than it appears to:
"When creating an MCS certificate for an installation through the MID, you will need to enter the full name of the Technical Supervisor. This is a mandatory step."
The MID is the MCS Installation Database. The Technical Supervisor "replaces the current Nominated Technical Person", and the change that matters is not the job title. It is that the role "is instead linked to individual installations" rather than to the business. MCS is explicit that the person "can be directly employed by the installer or sub-contracted."
Set that beside the 14-day rule. The certificate you must create within 14 days will require the full name of the specific person who supervised that specific installation. If your Nominated Technical Person was one named director, the answer was the same every time and nobody had to write it down. If supervision is subcontracted, or shared across two or three people depending on the week, the answer changes on every job — and it now has to be recorded per installation, by someone who was there.
That name is currently in nobody's system. It is not on the design. It is not necessarily on the purchase order. It is in the memory of whoever booked the day. Day 14 is a poor moment to start looking for a surname.
The surveyor's numbers and the certificate's numbers
This is the quietest break.
Somebody surveyed the property and produced a design: panel count, orientation, pitch, estimated yield. Somebody ordered the kit. Somebody fitted it — and on a fair proportion of jobs fitted something slightly different, because roofs are not drawings. Two fewer modules on the north-east plane. An array moved half a metre for a soil vent pipe nobody had photographed.
The certificate describes the system that exists. The design described the system that was intended. If the deviations are recorded when they are made, the certificate is a transcription. If they are not, it is an act of recollection, performed a fortnight later by somebody who was never on the roof, from photographs taken for a different purpose.
The failure here is not a late certificate. It is a certificate filed comfortably inside 14 days that describes a system subtly unlike the one on the roof.
What it looks like from the other end
To you the certificate is a compliance artefact. To the customer it is proof that the thing on their roof is real. When it does not arrive, they do not conclude that your office is busy.
Two real thread titles from r/SolarUK:
"Installer ghosting us post installation - documents missing?" — 27 October 2024
"What paper work should I have received from my installer?" — 28 January 2025
The second is the worse of the two. The first homeowner knows something is missing. The second does not know what to ask for, and is asking strangers on the internet what their installer owed them. Neither title describes a bad installation. Both describe a missing paper trail.
The definitive list of what must be handed over is set out in MIS 3002 and by your certification body. Check both, and do not take a document list off a blog, including this one. What is safe to say is that the pack and the certificate draw on the same facts. A firm reconstructing them on day 14 reconstructs them twice: once for MCS, once for the customer who is by then typing a question into Reddit.
The data already exists
The figures on the certificate are the figures from the design and the figures from commissioning. They already exist. They should not have to be re-entered from memory three weeks later by somebody who was not there. It is a workflow failure, not a character failure, and it is fixed at the point of capture, not the point of filing.
Solar Engine holds the design side of that record — the survey, the layout, the yield figures — in one place, so the numbers you certify are the numbers you designed rather than the numbers you recall. It does not file MCS certificates and it does not touch the MID. That part stays yours.
What to do this week
- Read the MCS reminder in the original, not in a group chat.
- Move your certificate trigger from invoice day to commissioning day. The clock starts at commissioning, so that is where the task should be created.
- Capture the Technical Supervisor's full name when you book the supervision, not when you open the MID. Subcontracted supervision is expressly permitted. Unrecorded supervision is a problem handed to your future self.
- Record as-built deviations on the day, on site, against the design. Two minutes on a roof, an afternoon in an office.
- Check MIS 3002 and your certification body for the definitive handover pack contents, and put that list where the person doing the paperwork can see it.
The rule has not changed. What is changing is that the certificate will depend on a fact — who supervised this job — that most firms have never had a place to write down. Give it a place before the transition reaches you.