Master the A&E Billing and Invoicing Process: A Step by Step Guide

Billing is the most under engineered process in most A&E firms. The work is delivered with rigor. The invoice goes out late, with errors, and gets paid 75 days later. Then the partners wonder why cash is tight.

This guide walks the full billing cycle for architecture and engineering firms, from the moment a contract is signed to the moment payment lands. The objective is simple: shorten the cycle, reduce the errors, and stop leaving money on the table.

The eight stages of an A&E billing cycle

Most billing problems trace back to a missing stage, not a missing tool. The full cycle has eight stages, each with a clear input and output.

1. Contract setup. Billing terms, schedule, and rate table loaded into the system on day one.
2. Time and expense capture. Staff log work daily against the right project and phase.
3. WIP review. Work in progress is reviewed weekly for accuracy before invoicing.
4. Pre bill review. PMs adjust hours, write offs, and narratives before the invoice is generated.
5. Invoice generation. The invoice is produced from approved WIP.
6. Internal approval. Partner or principal sign off if required by firm policy.
7. Client send and follow up. Invoice sent, receipt confirmed, follow up scheduled.
8. Collection and reconciliation. Payment received, AR cleared, revenue recognized.

Skip any one of these and the cycle stretches by 7 to 14 days on average.

Stage 1: Contract setup is where speed begins

Most billing delays start at signing, not at month end. If the project is set up in your system the same week the contract is signed, you bill cleanly. If the setup waits until first invoice, you discover scope, rate, and approval issues after the work is already done.

Capture these on day one.

• Billing schedule (monthly, milestone, percent complete).
• Rate table by role.
• Pass through markup percentage for consultants and direct expenses.
• Retainage if any.
• Required backup format (timesheets, narrative, photos).
• Approval chain on the client side.

Stage 2 and 3: Capture and WIP review

Daily time entry is not optional. Weekly time entry costs your firm cash. The simple math: if hours arrive Friday for the week, your billable WIP is on average four days stale, which means your monthly invoice is built on data that is already four days old when you start. Push for daily entry, with a soft Tuesday deadline for the prior week.

WIP review happens weekly. The PM looks at what was logged against this project. Anything coded wrong gets fixed in the same week, not at month end. Time tracking discipline is the foundation that makes the rest of the cycle fast.

Stage 4: Pre bill review separates good firms from bad ones

The pre bill is where most billing accuracy is won or lost. The PM reviews the draft invoice before the client ever sees it.

The four checks that matter.

1. Are the hours right. Spot check 10 percent of entries.
2. Is the narrative client ready. "Worked on project" gets edited to "Issued revised structural calcs for north tower."
3. Are the write offs intentional. Every hour written off is partner level money. It deserves a reason.
4. Is the format what this client expects. Some clients require AIA G702/G703. Others want a plain summary. Get it right the first time.

A clean pre bill means the invoice goes out the same day it is approved, not three days later after the back and forth.

Stage 5 and 6: Generate and approve

Generation should be a one click step. If your team is hand assembling invoices in Word from a spreadsheet, you have a tool problem. Connected accounting turns the generation into a reflex.

Internal approval is policy specific. Most firms require principal sign off above a fee threshold. Whatever your policy is, write it down and route it consistently. Ad hoc approval is where invoices sit for a week.

Stage 7: Send and confirm receipt

Email is not delivery. Many client AP teams have inbox rules that hide attachments. Send the invoice, then send a separate one line email asking the client to confirm receipt. The 12 second confirmation step prevents the "we never got the invoice" conversation 30 days later.

For larger clients, ask which portal they use (Ariba, Coupa, Open Asset, etc.). The portal upload is part of delivery, not after delivery.

Stage 8: Collection is a habit, not an event

Most firms collect reactively. The invoice goes out, then sits, then a partner asks "did we get paid for the X project" and the chase begins. The firms that hold a 45 day DSO are doing the opposite: collection is scheduled, not reactive.

The minimum cadence.

• Day 7 after send: friendly receipt confirmation.
• Day 30: first reminder, polite, with the invoice attached.
• Day 45: second reminder, name the partner who is following up.
• Day 60: partner phone call, not email.
• Day 90: formal collection conversation. At this point the project may need to slow down until the bill is current.

The DSO calculation

Days sales outstanding measures how long it takes to convert revenue into cash. The formula is simple: total accounts receivable divided by average daily revenue.

Most A&E firms run a DSO between 60 and 90 days. The strongest firms are at 45 to 55. Every 10 days you shave off DSO is real cash that frees up to pay staff and reinvest. DSO is one of the 10 financial KPIs every firm should track monthly.

The five mistakes that bleed cash

• Monthly billing across the board. Some clients pay faster on milestone or percent complete. Match the cadence to the contract.
• Letting write offs run unchecked. Each one is a profit margin reduction. Audit them quarterly.
• Inconsistent narrative quality. A vague description triggers client review and delay. A specific one closes the loop fast.
• Stale rate tables. If your rates have moved and projects are still being billed at last year's numbers, that is direct margin loss.
• No backup attached. Many AP departments will not pay without timesheets or narrative. Send it on the first try.

What good looks like 90 days in

After 90 days of running this cycle deliberately you should see three changes: invoices going out within five business days of month end, DSO trending down by at least 5 days, and write offs falling because pre bill review caught issues before send.

None of this requires a new tool. It requires the discipline to run the cycle as a real process. The firms that do this beat the firms that do not, every quarter, on the only number that matters: cash.