Electricians
What belongs on a electrical invoice
Four things that decide whether a electrical invoice gets paid or gets a phone call. The generator further down opens with the lines already in it.
Certificate and test work is a separate line from installation, because it is a separate legal thing. An installation certificate is a document you are signing your name to, it takes time, and a customer who sees it costed understands why they cannot have it for free when they later want it for a sale.
Consumer unit changes attract questions about “why is this so much when the part is £120”. The answer is on the invoice or it is on the phone: circuit-by-circuit testing, certification, and making good. Put the testing on its own line.
Where you have quoted and then found something notifiable, invoice the quoted work at the quoted figure and the extra as a clearly separate line with its own description. A quote silently exceeded is the single fastest way to lose a domestic customer.
Materials at trade with a stated markup is a defensible line. Materials at an unexplained number is an argument waiting to happen.
Where the customer is a landlord or an agent, the invoice needs the property address as well as the billing address. It is also the document that proves when the work was done, which is what an insurer asks for after a fire, so the date and the description are worth writing as though they will be read by a stranger years later.
The lines below are real work at plausible quantities, and deliberately carry no prices. A price is a local fact about a local market, and a made-up one would be worse than none.