Every engagement is written down before it starts: what is being built, in numbered lines, and a matching list of what is NOT included.
The exclusion list is not fine print and it is not defensive. Most arguments between a contractor and a client are about something one side assumed was in and the other assumed was out, and the only reliable cure is to write both lists at the same time.
Work changes. When it does, the change is written as its own document: what is being added or removed, what it does to the price, what it does to the date.
The original scope stays as it was and the change stacks on top of it. Nothing is quietly rewritten, and at the end of the job you can read the whole history in order.
A deposit is taken before work starts and is credited against the final total. Until it has been earned it is money owed back to you, not counted as ours the day it arrives.
Invoices then follow the agreed schedule, carry a real sequential number, and set out every line as a net amount, its tax rate, and its tax separately. Payment terms are agreed on the engagement and printed on the invoice.
If something on an invoice was wrong, it is corrected by a credit note that names the original and reverses exactly what it needs to. The original keeps its number and stays in the run.
That is slower than quietly amending a PDF, and it is the only version that still makes sense to your accountant, and to ours, a year from now.
Tax is worked out line by line and summarised by rate, never as one blended figure at the bottom.
Which rules apply depends on where you are, whether you are registered, and what kind of work it is, so the treatment is settled and stated in writing before the first invoice rather than assumed. We do not give tax advice and we do not file anything on your behalf.
An assistant can draft, price and assemble anything, right up to the moment before it becomes real. It cannot issue an invoice, send an invoice, or set a tax rate.
Those stay acts a person takes, because an issued invoice is a dated demand for money landing in someone else's accounts. The same rule governs everything else here, including what goes live on this site.
What a build costs depends on what it has to do, so there is no price list to read.
Tell us about the business on the get started page and what comes back is a written scope and a number, not a discovery call.