Time and cost billing by staff level
Engineering consultancies often bill on time and cost: hours recorded against the job by each person, multiplied by that person’s charge out rate. Listing hours by staff level, rather than one blended figure, shows the client that a drafter drew the plans and the principal reviewed them, and why the rates differ.
| Role | Usual tasks | Example rate (NZD per hour, excl. GST) |
|---|---|---|
| Principal engineer | Review, sign off, producer statements | $230 (example) |
| Senior engineer | Design and calculations | $185 (example) |
| Engineer | Modeling and member checks | $150 (example) |
| Drafter or technician | Drawings and markups | $110 (example) |
Engineering invoice template example for a structural design job
Below is one month’s invoice for the structural design of a two storey timber framed house in Christchurch. Amounts are examples in NZD, excluding GST. A fixed fee job would list agreed stages instead, but the site visit and disbursement lines would look much the same.
| Line | Qty | Example amount |
|---|---|---|
| Principal engineer, design review and sign off, hours | 4 | $920 (example) |
| Senior engineer, foundation and bracing design, hours | 14 | $2,590 (example) |
| Drafter, structural drawings, hours | 10 | $1,100 (example) |
| Site visit, foundation reinforcement observation | 1 | $380 (example) |
| Disbursement: geotechnical investigation by sub-consultant | 1 | $1,450 (example) |
Report progress against the fee estimate
Clients agree a fee estimate before work starts, so every invoice should answer the question they will ask: how much of it has gone? A short summary under the lines, showing the estimate, the amount billed to date and what remains, brings problems up early, while there is still time to talk about scope.
- “Fee estimate $9,800. Billed to date, including this invoice, $6,240. Remaining $3,560.”
- Scope changes, such as an added deck, billed as a variation with its own estimate.
- What is still to come, for example the PS1 once council questions are answered.
Producer statements, site visits and disbursements
A structural engineer invoice in New Zealand often carries lines other trades never use. Producer statements may form part of the design work (PS1) or the construction review at the end (PS4), and site observation visits sit in between. Bill each as a named line, so the client can match it to the building consent paperwork.
- PS1 for design, issued with the consent application, as its own line if your agreement prices it separately.
- Site observation visits by date and purpose, for example “foundation reinforcement before pour, 21 October”.
- PS4 for construction review at completion, once your observations are done.
- Disbursements: sub-consultants, council lodgement costs, travel and printing, at cost or with the agreed handling fee.
GST and taxable supply information in New Zealand
New Zealand GST is 15%. Since 1 April 2023, Inland Revenue has required taxable supply information instead of a formal tax invoice, although the familiar title is still fine to use. What you must show grows with the value of the job, and a design invoice like our sample sits in the top band.
Above $1,000, a GST registered client must be named along with one way to identify them, for instance their address, NZBN, phone or email. Every supply over $200 also needs your name and GST number (simply your IRD number), the date, what you supplied, and the price split into excluding GST, GST and including GST, or shown GST inclusive with a note saying so. A registered client who requests this for a supply over $200 is owed it within 28 days. Registration becomes compulsory at $60,000 of taxable turnover in 12 months. See the New Zealand invoice template for each band.
Monthly claims and starting from the sample
Work that runs over several months is easiest to bill on the same date each month, for hours and disbursements recorded to the end of the month before. Give each claim its own invoice number and repeat the job number and fee summary, so the client’s project manager can approve it quickly.
Open the engineering services invoice sample to start from the Christchurch design job above, set to New Zealand with 15% GST. Architects on the same build can use the architecture invoice, and the builder the construction invoice. See every invoice template, and if a claim goes unpaid, read our guide to following up an unpaid invoice.
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