For solar & heat pump installers

Invoicing for solar and heat pump installers

The panels, the inverter, and the cylinder are paid for at the wholesaler weeks before the client pays you. Ask for a deposit that covers the kit and leave the balance due on commissioning, send the MCS certificate and the handover pack with the invoice email, and set the VAT rate line by line when a job doesn’t sit on one.

30 days of everything, free. No card needed.

Survey to commissioning

From the survey to the money

1

Price the system as a quote

The array, the inverter, the cylinder, the scaffold, and the days on the roof, priced line by line and accepted on the client’s phone with no login. An accepted quote turns into a draft invoice carrying the same lines and prices. See how quotes work.

2

Take the deposit before the kit is ordered

A deposit as a percentage or a fixed amount, with its own due date, printed on the invoice next to the balance. The wholesaler gets paid out of the client’s money and the balance stays due on commissioning day. On a bigger commercial array, split the total into stages instead. See deposits and payment plans.

3

Send the invoice with the handover pack

The MCS certificate, the DNO paperwork, and the handover pack ride the same email as the invoice, as attachments. The client gets the bill and the documents in one message instead of asking for the pack a fortnight later, and the invoice itself prints as an A4 PDF with your logo.

4

Get paid, with the sums already done

Connect Stripe and a homeowner settles by card from the link before the scaffold comes down. Instant bank payment is there too, capped at £10,000. Fitting plots for a main contractor? Tick CIS and enter the labour figure, and the deduction comes off the labour alone on a CIS invoice, never the panels.

The rest of the week

Mixed rates, housebuilders, and the service round

A solar and heat pump business bills three kinds of client, and each one wants a different invoice: a homeowner paying for hardware you ordered before anyone paid you, a housebuilder or main contractor who takes a deduction off you, and a managing agent whose systems need a visit every year.

The kit covered before the order goes in

A deposit that covers the panels, the inverter, and the cylinder means the wholesaler is paid out of the client’s money rather than yours. Set it as a percentage or a fixed amount with its own due date, and Sendinvo chases the deposit first, then switches to the balance once it lands. On a commercial array, split the total into stages instead: deposit on order, scaffold and mounting, then the balance on commissioning and handover.

One job, more than one VAT rate

A heat pump going in with radiator upgrades, or a battery added to an array that is already on the roof, can land on more than one VAT rate. Tick “Set VAT per line” on a sterling invoice and each line carries the rate you give it, with a subtotal for each band and a total that agrees to the penny. Sendinvo does the arithmetic and nothing else here: which rate a line takes is your call, or your accountant’s. Raise a credit note against a mixed-rate invoice and each line credits at the rate it was billed at, so dropping the battery from the spec doesn’t move VAT from one band to another. See VAT per line.

Plots for a main contractor, netted down before it goes

Retrofit work for a housing association, or systems on plots for a housebuilder, goes out as a CIS invoice. Enter the labour figure and the deduction comes off that alone, so the panels, the mounting rail, and the cylinder keep their full value. If both companies are VAT registered, a domestic reverse charge tick box appears alongside CIS. Tick it and the invoice carries no VAT and the wording HMRC expects, and the main contractor pays the net amount.

Service visits that invoice themselves

An annual heat pump service, or a monitoring and cleaning visit on a commercial array, is the work that gets forgotten. Put it on a recurring schedule and Sendinvo raises the invoice and emails it on the date without you opening the app. Your standing files go with every one, so the public liability certificate a managing agent asks for is attached each time.

Chased, then charged

A housebuilder’s 60 days is your overdraft, and the wholesaler was paid months before that. Reminders go out at 1, 7, and 14 days past due unless you change them, and they stop the moment the money lands. If a sterling invoice to another business runs over, Sendinvo works out the statutory interest from the base rate you keep in settings, plus the fixed compensation the Act allows, £40 on a debt under £1,000. One click drafts a separate invoice for you to read before it goes.

See it in action

Have a click around the real app

The demo below is seeded with an electrical business, not a solar one, because that is the data we have. The work in it is the shape yours is: a materials deposit taken before an EV charger was ordered, a job billed in stages, a monthly round for a letting agent on a schedule, and an invoice past its date being chased.

sendinvo.com/invoices

A live demo seeded with an electrical business, not a solar one. Nothing you do here is saved or sent.

Worked examples

A heat pump for a homeowner, then plots for a main contractor

The first one puts the kit money in before you order. The second is subcontract work, with the deduction off the labour alone.

Invoice to a homeowner, air source heat pump and cylinder
Deposit, heat pump and cylinder on order £4,500.00 Paid
Balance, due on commissioning and handover £6,300.00 Next due
Total £10,800.00

The deposit has its own due date, so it is chased on its own and the wholesaler is paid before you order. Once it lands, the chasing moves to the balance and stops when that is paid. Both parts sit under £10,000, the ceiling Stripe puts on instant bank payment. The MCS certificate and the handover pack go out with the balance invoice, attached to the email beside the PDF.

The other one: an array on two plots for a housebuilder, where the deduction comes off you before the money arrives.

Invoice to a VAT-registered main contractor, CIS at 20%
Labour, install and commissioning, plots 7 and 8 £3,200.00
Panels, inverter, mounting rail, and cable £5,400.00
Subtotal £8,600.00
VAT (domestic reverse charge) £0.00
Total £8,600.00
CIS deduction (20% of the labour) −£640.00 Labour only
Amount due £7,960.00

The deduction is 20% of the £3,200.00 labour, not of the £8,600.00 total, so the panels, the inverter, and the rail keep their full value. Under the reverse charge the invoice charges no VAT and prints the wording HMRC expects, stating the VAT the contractor accounts for at their end, worked out at the rate you set on the invoice. When the £7,960.00 lands, the invoice settles in full and the deduction is booked as a non-cash settlement.

Questions

Good to know

Can I take a deposit that covers the panels and the inverter?

Yes. On a draft invoice, ask for a deposit as a percentage or a fixed amount and give it its own due date, so the kit is paid for before you order it and the balance falls due on commissioning. The invoice prints both, so the client can see what pays for the hardware and what pays for your days on the roof. Sendinvo chases the deposit until it is paid, then moves on to the balance.

Can I send the MCS certificate and the handover pack with the invoice?

Yes, as attachments on the invoice email, alongside the invoice PDF. They don’t print on the invoice document itself. One email carries 10 MB across up to 10 files with the invoice PDF counted in, which is room for the certificate, the handover pack, and the commissioning readings.

Can one invoice carry more than one VAT rate?

Yes. On a sterling invoice, tick “Set VAT per line” and every line carries the rate you give it, with a subtotal for each band and a total that agrees to the penny. Sendinvo doesn’t decide which rate a line should take and it doesn’t know your VAT position. That one is for you or your accountant.

Does Sendinvo work out CIS on plots for a main contractor?

Yes. Set your rate once in company settings: 20% for a registered subcontractor, 30% if you’re not registered, or 0% for gross payment status. Tick “Apply CIS deduction” on a sterling invoice and enter the labour figure, and the deduction comes off that alone while the panels, the inverter, and the cylinder keep their full value. The invoice shows the gross total and the net amount the main contractor pays, and when that net amount lands the invoice settles in full.

Can annual heat pump services go out on a schedule?

Yes. Put the visit on a recurring schedule and Sendinvo raises next year’s invoice and emails it on the date without you opening the app. Weekly, every two weeks, monthly, quarterly, and annually are all available, and a schedule can end on a date or after a set number of invoices. When your reminders are on, every invoice a schedule sends is enrolled in them, so a managing agent who forgets is chased like anyone else.

Do you notify MCS or the DNO, or file anything with HMRC?

No. Sendinvo works on the invoices you send. It works out the CIS deduction, prints the reverse-charge wording, and carries your certificate and handover pack as attachments on the email. It doesn’t register an installation with MCS, submit a DNO application, verify subcontractors, or send a CIS300. Those stay where you do them today, and the CIS return stays with your accountant.

Kit money up front, the balance on commissioning

30 days of everything, free, no card needed. After that it’s £20 a month for one person and £5 a month for anyone else you put on the account, with every feature included.