Do I have to change software?

Usually not. If what you use can record a VAT rate per job and separate materials from labour, it is fine. We would only propose a move where the current setup makes the VAT or CIS position impossible to evidence, and then we do it once rather than incrementally.

What about Making Tax Digital?

Keeping the records digitally through the year is what makes it a non-event rather than a deadline. If you are already on digital bookkeeping for VAT, the extension to income tax is mostly a change of filing rhythm rather than a change of work.

Can you do just the year end?

Yes, and plenty of installers start there. The trade-off is that a year end built from a shoebox cannot evidence a VAT rate decision made ten months ago, so it is the cheaper option that carries the more expensive risk.

Solar trade guidance

Bookkeeping and Accounts for Solar Firms

Written and reviewed by the Solar Installer Accountants editorial team. Last reviewed 22 August 2026.

Solar installer reviewing job paperwork beside a work van and scaffolded British home

Bookkeeping through the year and the accounts at the end of it, kept in a shape that makes the rest of the compliance provable rather than reconstructed.

For a solar firm this is not a commodity. The records have to carry the VAT rate applied to each job and the split between labour and materials, because both of those are what an HMRC question turns on.

What It Covers

Sales and purchase ledgers kept current, bank reconciliation, and job-level records that show what was installed where and at what VAT rate. Panels, inverters and batteries tracked as purchases so the materials position is clear, which matters both for margin and for the CIS deduction where you are subcontracting.

At the year end, the accounts themselves: statutory accounts and the corporation tax return for a company, or the accounts behind Self Assessment for a sole trader.

Why the Records Shape the Tax

Two of the biggest numbers in a solar business are decided by record keeping rather than by tax planning. The first is the VAT rate per job, which needs evidencing at the time. The second is the labour and materials split on subcontract invoices, because CIS is deducted on labour, not on the materials you paid for directly.

On a panel-heavy job that split is the difference between a deduction taken on the whole invoice and one taken on a fraction of it. Invoices that itemise it properly put the cash back in your account months earlier.

How It Runs

We work in whatever you already use, provided it can carry a per-job VAT rate. Where it cannot, we will say so and move you once, at the start, rather than living with a workaround.

Records come across on an agreed cycle. You get management figures during the year rather than only meeting your numbers eleven months late.

What It Costs

A fixed fee based on transaction volume and whether the year end is included. Quoted before we start.

To get a price, tell us about your solar work and roughly how many jobs a month you invoice.