Every month, in architecture firms and engineering offices, billable hours disappear. Not stolen. Not disputed. Simply forgotten. Not entered, not validated, not billed. This silent phenomenon represents one of the most common -- and most preventable -- cash flow leaks in the sector.
The solution is not to work more. It's to implement a structured workflow that transforms every hour worked into an invoice line, then into a verified collection. Six steps, no improvisation, zero oversights.
The Money That Leaks: How Many Billable Hours Slip Through the Cracks Each Month?
Studies on billing in consulting and project management professions converge: between 10 and 20% of billable hours are never billed. Not because the client refuses, but because nobody identified them as billable.
Key figure: A 6-person firm billing an average of EUR 48/h loses between EUR 15,000 and EUR 30,000 per year in unbilled hours. That's the equivalent of half a loaded salary evaporating.
The causes are always the same:
- No systematic process: billing depends on the director's memory
- Forgotten time: small interventions (client calls, technical emails, quick site visits) are never entered
- Unclear billing status: nobody knows what has been billed, what remains to be billed, what is awaiting payment
- No regular review: months pass without verification, hours accumulate in a blind spot
The problem is not technical. It's organizational. And it's solved with a clear workflow, applied with regularity.
The Ideal 6-Step Workflow: From Time Entry to Collection
Here is the complete path that an hour of work must travel to become a euro collected in the firm's account:
┌─────────────────┐
│ 1. DAILY │ Each team member, every day
│ ENTRY │
└────────┬────────┘
▼
┌─────────────────┐
│ 2. WEEKLY │ Project manager, every week
│ VALIDATION │
└────────┬────────┘
▼
┌─────────────────┐
│ 3. MONTHLY │ Management, every month
│ REVIEW │
└────────┬────────┘
▼
┌─────────────────┐
│ 4. TAG AS │ Status "to be billed"
│ BILLABLE │
└────────┬────────┘
▼
┌─────────────────┐
│ 5. EXPORT AND │ Generate invoice
│ ISSUE │
└────────┬────────┘
▼
┌─────────────────┐
│ 6. PAYMENT │ Collection confirmed
│ TRACKING │
└─────────────────┘
Each step has an owner, a frequency, and a specific action. If any of the six is neglected, the pipeline clogs and oversights accumulate. Let's detail each one.
Step 1 -- Daily Entry: The Raw Material
Time entry is the starting point of the entire workflow. Without reliable raw material, the rest of the process is built on sand.
The principle is simple: each team member enters their hours the same day, at end of day. Thirty seconds is all it takes when you've just lived through the day. Thirty minutes won't be enough if you wait until Friday to reconstruct the entire week from memory.
The minimum information to record:
- The project concerned
- The mission phase (sketch, APS, APD, tender documents, construction, etc.)
- The actual duration spent
- A short note describing the activity (optional but valuable for billing)
Common mistake: Batching entry at the end of the week. Memory distorts durations: long meetings are underestimated, small tasks disappear. An internal study at a consulting firm showed that entry delayed by more than 48 hours underestimates actual time by 25 to 35%.
The golden rule: same day, every day. This is non-negotiable. If entry takes more than 30 seconds, the tool is misconfigured -- it's not that the discipline is too demanding.
Key takeaway: Daily entry is not a surveillance tool. It's the first link in a chain that protects the firm's cash flow. Every team member who enters their time directly contributes to the financial health of the organization.
Step 2 -- Weekly Validation: The Quality Filter
Each week, the project manager reviews their team's entries. This check takes 10 to 15 minutes and catches errors before they contaminate the billing.
The checkpoints:
- Correct project: are hours assigned to the right file? (entry errors between similar projects are frequent)
- Correct phase: is the mission phase right? (billing tender documents against the APS phase distorts tracking ratios)
- Consistent volume: 12 hours on a simple plan update is suspicious. Zero hours on an ongoing construction site, likewise.
- Completeness: have all team members entered? Spot empty days.
The project manager validates correct entries and returns those that raise questions, with a comment specifying what needs correction.
Common mistake: Validating in bulk without checking. The automatic stamp creates an illusion of control. If validation filters nothing, it serves no purpose. Better 10 minutes of real attention than cosmetic validation.
This is also the step where monthly billing preparation begins: the project manager notes projects approaching a billable milestone or a fee amendment to trigger.
Step 3 -- Monthly Review: The Billing Checkpoint
Once a month, management organizes a billing meeting. Target duration: 30 minutes. No more, if the upstream workflow has been followed.
The objective is to review all active projects and answer three questions for each:
- What is billable? Validated hours not yet billed, milestones reached, planned deposits
- What has already been billed? Cumulative amount, comparison with the project budget
- What is awaiting payment? Invoices issued but not yet collected
This meeting is the moment of truth. This is where you detect drifting projects -- too many hours consumed relative to budget, late invoices, unbilled phases piling up.
Common mistake: Skipping a month. "We're swamped, we'll do the billing next month." Result: two months of hours to sort through, forgotten details, and a cash flow gap that worsens. Monthly regularity is the pillar of the entire system.
Key figure: Firms that hold a monthly billing review reduce their unpaid invoices by 40 to 60% compared to those that bill "when they think of it." The effect is mechanical: bill early, get paid early.
To dig deeper into project-by-project profitability, this monthly review provides the essential data.
Step 4 -- Tagging "To Be Billed": The Trigger
After the monthly review, time entries that have been validated and identified as billable must be explicitly tagged with a "to be billed" status.
This tagging is crucial: it creates a visible billing pipeline. At any time, you know how many hours are waiting to be turned into an invoice, for what amount, on which project.
Tagging also serves as a clear boundary between:
- Entered time (raw, potentially incomplete)
- Validated time (verified by the project manager)
- To-be-billed time (approved by management for issuance)
- Billed time (included in an issued invoice)
Without this distinction, everything gets mixed up. Nobody knows what has been billed, what is pending, what was deliberately excluded. Oversights become inevitable.
Common mistake: Not tagging entries, telling yourself you'll remember. Three months later, nobody knows whether the 40 hours from March on the Duval project were billed or not. Without explicit status, doubt always favors the oversight.
Key takeaway: Tagging is not a superfluous administrative step. It's the mechanism that transforms time tracking into a billing tool. A good time management tool enables this tagging in a few clicks, with a traceable history.
Step 5 -- Export and Invoice Issuance
Hours tagged "to be billed" are now ready to become an invoice. This step consists of:
- Generating a billing report: list of hours by project, by phase, with calculated amounts (hours x hourly rate)
- Verifying amounts: comparing with the contract, deposits already paid, any caps
- Issuing the invoice: via the accounting software, incorporating the report elements
- Updating the status: hours move from "to be billed" to "billed," with the invoice number as reference
The billing report (PDF or CSV) serves as the supporting document in case of client questions. It details what is billed, why, and on what basis. It's a tool for transparency as much as for management.
Common mistake: Rounding down "to be nice" or "to make a round number." A firm that systematically rounds 8.5 hours down to 8 hours loses 6% of its billable revenue. Over the year, across multiple projects, that's thousands of euros evaporated through excessive politeness. If the time was spent and validated, it should be billed.
For lump-sum missions, the logic is different but the workflow remains the same: the time report serves to verify the project's profitability and to trigger amendments when actual time significantly exceeds the budget.
Step 6 -- Payment Tracking: The Final Loop
Issuing an invoice is not enough. You must ensure it is paid. This last step closes the workflow loop.
Tracking includes:
- Recording the issue date and payment due date (generally 30 days)
- Verifying collection: reconciling the bank statement with issued invoices
- Marking as paid when payment is received
- Following up from the first day of delay, then at regular intervals
The payment tracking table must be viewable at a glance: how many invoices are pending, total amount, which clients are late.
Common mistake: Not following up. Out of awkwardness, lack of time, forgetfulness. Result: payment terms that silently lengthen. A client who pays at 30 days without follow-up pays at 60 days when nobody's watching, then 90, then... never.
Key takeaway: Following up is not an aggressive act. It's a normal professional practice. A courteous email at day 31 reminding of the invoice is sufficient in 80% of cases. What matters is doing it systematically, not occasionally.
The Monthly Billing Checklist
Here is the complete checklist to follow each month. Print it, display it, integrate it into your management routine.
- 1. Check entry completeness -- Have all team members entered their hours for the entire month?
- 2. Identify empty days -- Spot days with no entries and request catch-up
- 3. Validate hours by project -- Has the project manager validated all entries in their scope?
- 4. Compare actual hours vs budget -- For each active project, where do we stand relative to the hour budget?
- 5. Identify overruns -- Do any projects require a fee amendment?
- 6. Tag hours "to be billed" -- Have all the month's billable hours been tagged?
- 7. Generate billing reports -- One report per project, with hour and amount details
- 8. Issue invoices -- Has each "to be billed" report resulted in an invoice?
- 9. Check pending payments -- Which invoices from previous months remain unpaid?
- 10. Follow up on delays -- Has each overdue invoice been followed up on?
This checklist takes only 30 to 45 minutes if the upstream workflow has been followed. It's the most profitable time of the month: every minute invested here translates directly into recovered cash flow.
Key figure: Firms that apply a monthly billing checklist see a 70 to 90% reduction in billing oversights from the second month of implementation. The effect is immediate and cumulative.
Conclusion: A Simple Workflow, Immediate Results
The 6-step workflow is nothing revolutionary. Enter, validate, review, tag, bill, collect. Six verbs, six actions, six moments in the month. No step requires more than 30 minutes.
What makes the difference is not the system's complexity. It's its regularity. A workflow applied every week and every month mechanically eliminates oversights. Hours no longer disappear into blind spots. Invoices no longer linger for months. Payments are tracked and followed up.
For a 6-person firm, moving from approximate tracking to this structured workflow potentially represents EUR 15,000 to EUR 30,000 in recovered revenue per year. Without working a single extra hour. Just by billing what's already been done.
The first step is always the same: ensuring that every hour worked is entered, every day, by every team member. Everything else follows from that.