Engineering Invoice Template: Phases, Hourly and % Complete

Quick answer: An engineering invoice template bills a client for professional engineering services. It references the project, contract and billing period, then shows fees by phase with percent complete, hours by role and rate, or both, plus reimbursable expenses, subconsultant costs, previous billings, retainage and the amount due this period.

Consulting engineers bill differently from most service businesses. A single project can run for a year or more across several design phases, involve subconsultants and pass-through permit fees, and be invoiced monthly against a fixed fee for each phase. Owners and their project managers review engineering invoices closely, so the format needs to show the contract value, what was earned this period and what remains.

This guide explains the main engineering fee structures, how to invoice by phase and percent complete, how to present hourly rates by role and reimbursables, and how to handle retainage. It includes a full engineering invoice example with real arithmetic. You can recreate it in our free invoice generator.

What is an engineering invoice?

An engineering invoice is a progress bill from a professional engineering firm or licensed Professional Engineer (PE) for design, analysis, inspection or consulting work. Civil, structural, mechanical, electrical, plumbing (MEP), geotechnical and environmental engineers all use one. Unlike a contractor's invoice, it bills professional services, not construction work, though the structure is similar to progress billing in construction.

Engineering is a large profession: the US Bureau of Labor Statistics profiles civil engineering alone in its Occupational Outlook Handbook. Firms range from solo PEs doing residential structural letters to multi-office firms billing public agencies. The invoice principles are the same.

Common engineering fee structures

Fee structure	How it is invoiced	Typical use
Lump sum by phase	Each phase has a fixed fee; bill monthly by percent complete	Building design, site development
Hourly (time and materials)	Hours x role rate plus expenses, often with a not-to-exceed cap	Studies, uncertain scope, construction administration
Cost plus fixed fee	Direct labor x overhead rate, plus a fixed profit fee	Federal and state agency contracts
Multiplier	Direct salary cost x agreed multiplier	Some private and institutional clients
Percentage of construction cost	Fee is a percent of estimated or actual construction cost	Less common now; some building projects
Unit or per-item	Fixed price per inspection, test or report	Special inspections, materials testing, letters

Architects use similar structures; the architect invoice template covers AIA-style phase billing from the design side. For general professional services, the consulting invoice template is a simpler starting point.

How to invoice PE services by phase

Building and site projects usually follow standard phases. Each gets a share of the total fee in the contract:

1. Study or preliminary design: site investigation, feasibility, code review.
2. Schematic design (SD): basic systems and layout.
3. Design development (DD): sizing, coordination, outline specifications.
4. Construction documents (CD): stamped drawings, calculations and specifications for permit and bid.
5. Bidding and permitting: answering questions, permit comments.
6. Construction administration (CA): submittal and RFI review, site visits, punch lists.

Each month, estimate percent complete per phase, calculate the fee earned to date and subtract previous billings. Keep the estimate honest: if drawings are 40% done, do not bill 70% because the budget is tight. Owners compare billing with deliverables, and over-billing early creates disputes later.

Hourly rates by role

For hourly work, list each labor category with its contract rate. Rates depend on region, firm size and specialty, so the figures below are illustrative only, not a market survey:

Labor category	Illustrative billing rate
Principal / senior PE	$210 to $260 per hour
Project engineer (PE)	$150 to $190 per hour
Staff engineer (EIT)	$110 to $140 per hour
Designer / CAD technician	$90 to $120 per hour
Field technician / inspector	$80 to $110 per hour
Administrative	$65 to $85 per hour

Most firms publish a rate schedule attached to the contract and update it each January. The contract should say whether rates can change mid-project.

Reimbursables and subconsultants

Reimbursable expenses are costs the firm pays on the project's behalf. Common examples are mileage and travel, large-format printing, courier fees, permit and plan review fees, lab testing and subconsultant invoices. Mileage is often billed at the IRS business rate (72.5 cents per mile for January to June 2026 and 76 cents from July 1, 2026, per irs.gov). See the mileage invoice guide for formatting.

Subconsultants (survey, geotechnical, MEP, landscape) are often billed with a markup for coordination and risk, commonly stated in the contract as a percentage. Show cost and markup separately, and attach backup if required. Our guide to reimbursable expenses on invoices explains how to present receipts.

What should an engineering invoice include?

• Firm name, address, license or certificate of authorization number where your state requires it on business documents.
• Client name, project name and number, contract or task order number, PO.
• Invoice number, date and billing period (for example, services through October 31, 2026).
• Fee summary by phase: contract amount, percent complete, earned to date, previously billed, this invoice.
• Hourly section for any T&M tasks.
• Reimbursables and subconsultants with markup.
• Additional services authorized by amendment, listed separately.
• Retainage withheld, if applicable.
• Total due, terms and payment instructions.

Example engineering invoice (percent complete plus hourly)

A civil engineering firm bills a developer for a site plan. All names and figures are fictional.

Crestline Civil Engineering, PC | 1200 Grant Avenue, Denver, CO 80203
Invoice: CCE-24117-07 | Issued: October 31, 2026 | Services through: October 31, 2026 | Due: November 30, 2026
Client: Aspen Ridge Partners LLC | Project: Aspen Ridge Townhomes, No. 24117 | Agreement: dated March 2, 2026

Lump sum phases

Phase	Fee	% complete	Earned to date	Previously billed	This invoice
Preliminary design	$12,000	100%	$12,000	$12,000	$0
Schematic design	$18,000	100%	$18,000	$18,000	$0
Construction documents	$42,000	65%	$27,300	$16,800	$10,500
Permitting	$8,000	20%	$1,600	$0	$1,600
Subtotal	$80,000		$58,900	$46,800	$12,100

Hourly additional services (Amendment 1, drainage study)

Labor category	Hours	Rate	Amount
Project engineer (PE)	14	$175.00	$2,450.00
Staff engineer (EIT)	22	$125.00	$2,750.00
Subtotal			$5,200.00

Reimbursables

Item	Amount
Geotechnical subconsultant (invoice attached) $3,400.00 + 10% markup	$3,740.00
Plan review fee paid to county	$650.00
Mileage, 84 miles x $0.76	$63.84
Subtotal	$4,453.84

Invoice summary

Item	Amount
Lump sum phases	$12,100.00
Hourly additional services	$5,200.00
Reimbursables	$4,453.84
Total due this invoice	$21,753.84

Fee remaining on lump sum phases after this invoice: $80,000 - $58,900 = $21,100.

How the percent complete math works

Construction documents are worth $42,000. At 65% complete, earned to date is $42,000 x 0.65 = $27,300. Last month the phase was 40% complete, so $16,800 was already billed. This month's charge is $27,300 - $16,800 = $10,500. The same logic applies to every phase, so the client can check each number against the drawings they have seen.

Worked example: cost plus fixed fee and multiplier billing

Public agencies and some institutional owners do not pay a flat hourly rate. Instead they reimburse the firm's actual salary cost, an audited overhead rate and a fixed fee for profit. Here is how one month might look, using illustrative numbers:

• Direct labor (actual salaries for hours worked): $14,000
• Overhead at an audited rate of 150% of direct labor: $14,000 x 1.50 = $21,000
• Total labor cost: $14,000 + $21,000 = $35,000
• Fixed fee: the contract sets profit at $40,000 for the whole job; with the work 20% complete this month, $40,000 x 0.20 = $8,000
• Direct expenses: $1,200
• Invoice total: $35,000 + $8,000 + $1,200 = $44,200

A multiplier contract is similar but simpler. If direct salary cost is $14,000 and the agreed multiplier is 3.0, the labor billing is $42,000, with expenses added separately. The multiplier covers overhead and profit together. In both cases, the invoice must show the components so the agency can audit them, and you need timesheets that support every hour.

What owners check when they review an engineering invoice

Owner project managers, lenders and public agencies review engineering invoices against a checklist, whether written or not. Before sending, check that:

1. The contract value matches the signed agreement plus approved amendments, with no unauthorized increases.
2. Percent complete matches the deliverables they have seen (drawing sets, reports, permit submittals).
3. Previously billed amounts match what they have recorded as paid or pending.
4. Hourly tasks stay within any not-to-exceed limit, with a warning if they are close.
5. Reimbursables have backup and fall within the allowed categories.
6. The invoice is addressed to the right entity, often a single-purpose LLC for the project.
7. Lien waivers are attached if the lender requires them; see our lien waiver guide.

Public clients often have their own invoice forms and pay under state or federal prompt payment rules. For federal work, the Prompt Payment Act sets when interest accrues on late payments, and our guide on how to invoice the federal government walks through the systems involved.

Retainage, final invoices and late payment

Some owners hold back a share of each design invoice, often 5% or 10%, until a phase or the whole project is complete. If that applies, add a line below the invoice total: "Less retainage at 10%: -$2,175.38", and show cumulative retainage held to date. When the condition is met, send a separate final invoice that releases the retained amount and references every invoice it came from.

Close-out invoices should also confirm that all phases are at 100%, all reimbursables are billed and no further amendments are pending. Owners appreciate a statement such as "This is the final invoice for Agreement dated March 2, 2026; no further fees are due other than retainage listed above."

For late payment, rely on the contract. Industry agreements commonly let the engineer charge interest on overdue balances and suspend services after written notice if invoices remain unpaid. A suspension of design work is a serious step, so send reminders first and keep a record. Our guide to late payment fees explains how to word interest charges, and the article on mechanics liens explains when design professionals may have lien rights, which vary by state.

How to create an engineering invoice, step by step

1. Pull the contract fee by phase and the approved amendments.
2. Get percent complete from each project manager, with a short note on progress.
3. Export hours for any hourly tasks by labor category.
4. Collect subconsultant invoices and expense receipts.
5. Build the invoice in the invoice generator: header, project references, phase table, hourly lines and reimbursables.
6. Number invoices by project and sequence, such as 24117-07; the invoice number generator can help.
7. Add a brief progress narrative and send the PDF with backup by the date the client's AP cycle needs.

Common engineering invoicing mistakes

• Front-loading percent complete. It erodes trust and leaves little fee for late phases.
• Billing additional services without an amendment. Get written authorization first; our change order guide shows how.
• Mixing reimbursables into labor. Keep them separate with receipts.
• Forgetting the previous billings column. Without it, the client cannot reconcile.
• Ignoring retainage. If the owner holds back a percentage, track it and send a retainage release invoice at completion.
• Late invoices. Missing the client's monthly cutoff can add 30 days to payment.

Licensing and seal rules vary by state board; this guide is general information, not legal advice.

A clear engineering invoice template shows the contract value, percent complete by phase, hourly work, reimbursables and the amount due, so owners can approve it without a call. Our invoice generator is free, needs no sign-up and creates the PDF in your browser, which makes it a fast way to produce consistent progress invoices for every project.