Architect's Fee Proposal: Structure and Legal Mentions

An independent architect recently told us he loses almost an entire evening on every new project reformatting his fee proposal, without ever being quite sure he included every mandatory mention. The document went out anyway, because the client was waiting for an answer. It's a common situation: the architect's fee proposal (devis) is the first contractual document in the relationship with a client, yet it's often treated as a mere administrative formality, copied from one project to the next without ever being properly checked.

This article details what an architect's fee proposal must contain to be compliant, the three ways to structure fees in project management (maîtrise d'œuvre), and a method for building it without starting from scratch on every engagement.

Summary

1. A document with legal weight, not a formality
2. The three ways to price an engagement
3. The mentions that make a proposal compliant
4. Building your proposal step by step
5. When a simple proposal isn't enough
6. What we see among independent architects
7. Training to make these documents reliable
8. Frequently asked questions

A document with legal weight, not a formality

An architect's fee proposal is not just a price estimate: it is a pre-contractual document that becomes binding as soon as the client writes "Bon pour accord" (approved) on it. From that moment on, it sets the amount of fees, their breakdown, and commits the architect to the scope described. A mistake or an omission at this stage carries through the rest of the engagement, including the deposit and final invoices that follow it and generally reuse its number and breakdown.

What changes once it's signed

Before signature, the proposal commits to nothing: it's an offer. Once signed "Bon pour accord," it becomes the contractual reference for fees, and any substantial change to the scope (an extended program, an additional phase) should in principle trigger a formal amendment (avenant) rather than a simple verbal adjustment. This is the framework that makes precision matter from the very first version: a vague proposal today becomes a billable disagreement six months from now.

The legal framework that applies

In France, invoicing for professional services — which an architect's engagement falls under — is governed by article L441-9 of the Commercial Code, which requires a list of mandatory mentions on billing documents, supplemented by article 289 of the General Tax Code for VAT calculation. The proposal isn't yet an invoice, but it carries most of these mentions in advance — which is what later lets the deposit invoice reference it without retyping everything. The French National Council of the Order of Architects also notes that an architect's fees are freely negotiated with the client, but the contract must unambiguously state the payment method chosen and its amount.

The three ways to price an engagement

An architect can price fees in three ways, which can be combined in a single proposal: a single lump-sum fee, a breakdown across the standardized phases of project management, or an hourly rate. The choice depends less on personal preference than on the nature of the engagement and what the client needs to be able to track during construction.

The lump-sum fee

A single before-tax amount covers the whole engagement, with no phase breakdown. It's the most legible option for the client, but it assumes a stable, well-defined scope from the outset: any evolution of the program during the engagement forces a negotiated amendment rather than an adjustment to a line in the fee table.

Breakdown by project-management phase

Project management (maîtrise d'œuvre) splits into nine standardized phases: esquisse (ESQ, sketch), avant-projet sommaire (APS, preliminary design), avant-projet définitif (APD, final preliminary design), projet (PRO, design development), dossier de consultation des entreprises (DCE, tender documents), assistance aux contrats de travaux (ACT, contract assistance), visa des études d'exécution (VISA, execution-study review), direction de l'exécution des travaux (DET, site supervision), and assistance aux opérations de réception (AOR, handover assistance). Spreading fees across these nine phases, each with its own percentage, lets the client track the engagement's progress item by item, and lets the architect invoice each stage without waiting for the project to finish. When fees are calculated as a percentage of the works amount, they're adjusted to the final amount recorded at handover.

Time spent

An hourly rate per contributor (architect, drafter) multiplied by an estimated number of hours. The amount shown remains a non-binding estimate: actual billing is based on the time genuinely spent, evidenced accordingly. This method suits consulting engagements or one-off expert assessments, whose scope is hard to pin down in advance.

The mentions that make a proposal compliant

A proposal can be perfectly priced and still be non-compliant if it's missing a mandatory mention. These mentions don't vary from one project to the next: fixing them once, in a reusable template, avoids improvising them on every new engagement.

Identity, VAT, and insurance

A compliant architect's fee proposal states the issuer's full identity (name or company name, address, SIRET number, intra-EU VAT number), their registration number with the Order of Architects, and their professional indemnity insurance details, along with the client's full identity. VAT on an architect's intellectual services is 20%; it's calculated on the before-tax amount, and the amount including all taxes is obtained by multiplying that before-tax amount by 1.20, rounded to the nearest euro cent.

Validity and signature

The proposal states a validity period — three months is the most common duration absent any other agreement — beyond which the prices shown are no longer guaranteed. Finally, it carries a signature block with the "Bon pour accord" mention, dated by the client: it is that signature, and that signature alone, that turns the offer into a commitment.

Building your proposal step by step

Step 1: gather the issuer's information. Name or company name, address, SIRET number, intra-EU VAT number, Order of Architects registration number, professional indemnity insurance (company and policy number). This information doesn't change from one project to the next: gathering it once in a reusable template avoids re-entering it on every proposal.

Step 2: describe the engagement precisely. Purpose of the proposal, detailed description of the services, estimated works amount if fees are calculated as a percentage, optional missions (land survey, RE2020 thermal study, OPC/coordination mission) priced separately from the base scope rather than buried inside a lump sum.

Step 3: choose and build the billing method. Lump sum, phase breakdown, time spent, or a combination of the three — consistent with what was discussed verbally with the client, so the written document surprises no one.

Step 4: calculate VAT and the total amount. VAT equals the before-tax amount multiplied by 0.20; the amount including all taxes equals the before-tax amount multiplied by 1.20; both rounded to the nearest cent.

Step 5: number the proposal and set a validity period. Chronological numbering (for example P-2026-001) and a displayed validity period prevent an old proposal from being signed at an outdated rate, or a dispute arising over the exact issue date.

Step 6: add the signature block. The "Bon pour accord" mention, dated and signed by the client, is what makes the proposal binding. Without it, even the most carefully prepared document remains a simple offer.

When a simple proposal isn't enough

It has to be said plainly: a single-billing-method proposal doesn't fit every situation. An engagement involving several clients acting jointly (a co-ownership association, a group of residents) often calls for a finer contractual breakdown than a standard proposal can carry on its own, and benefits from a legal review before it's sent. Likewise, an engagement whose program is still unsettled at the time of pricing — a client still torn between an extension and adding a floor, for instance — doesn't sit well with a lump sum: time-based billing, or a phase breakdown with a first batch limited to the sketch phase, protects the architect better against an unanticipated change of scope. A proposal, however complete, also doesn't replace a proper project-management contract for the largest engagements: it's the priced foundation for one, not a full legal substitute.

What we see among independent architects

In the conversations we have with independent architects about their day-to-day tools, the bottleneck is almost never the pricing calculation itself: an architect knows how to price an engagement, and knows their rates and margins. What costs time is reformatting the document on every new project — finding the last version used, checking that no mandatory mention has gone stale since, adapting a fee table built for a lump sum to an engagement that, this time, needs to be priced by phase. It's repetitive, low-value work, not a skills gap — and it's exactly the kind of task a well-built document template, or a tool that applies it automatically, removes without taking anything away from the professional judgment that still rests entirely with the architect.

Training to make these administrative documents reliable

Setting a fee-proposal template once and for all isn't always enough: you still need to know how to use the right tools to keep it working project after project without losing time again. It's a concrete use of AI for architecture professionals, alongside more visible uses like rendering or sketching. For an architect practicing as a freelancer (a profession under NAF code 7111Z), FIFPL covers part of the cost of a Qualiopi-certified training course under 2026 criteria set at €300 per day and €900 per year, with e-learning capped at 50% of the daily rate. This is funding to apply for before training starts, not after.

Frequently asked questions

Must an architect's fee proposal state the Order of Architects registration number?

Yes, it's one of the expected mentions on an architect's fee proposal, alongside the issuer's full identity and professional indemnity insurance details. Its absence doesn't automatically invalidate the document on strictly contractual grounds, but it deprives the client of information they're entitled to expect from a regulated professional, and that an informed client — or an OPCO reviewing a funding file tied to the engagement — may request. In practice, the simplest approach is to build it into the reusable proposal template once and for all, rather than having to check for it on every new document.

What's the difference between a proposal and a deposit invoice?

The proposal is a pre-contractual document: it offers a fee amount and becomes binding only once the client signs it. The deposit invoice, by contrast, is issued after signature, at the actual start of the engagement, and is a full accounting document with its own mandatory mentions (a due date, for instance) that the proposal doesn't carry. The deposit invoice generally reuses the number and breakdown of the proposal it stems from.

How do you calculate VAT on an architect's fee proposal?

VAT on an architect's intellectual services is 20%. It's calculated by multiplying the before-tax amount by 0.20, and the amount including all taxes is obtained by multiplying that same before-tax amount by 1.20. Both results are rounded to the nearest euro cent and must appear as distinct lines on the document, alongside the before-tax amount.

Do you have to pick a single billing method per engagement?

No, the three methods (lump sum, phase breakdown, time spent) can be combined within a single proposal. A common case is pricing the core project-management engagement by phase, then adding a separately-priced, time-based line for an optional mission, such as an additional study requested during the project. What matters is that the proposal clearly distinguishes what falls under each method, so no ambiguity remains when it comes time to bill.

Does an architect's fee proposal have a legal validity period?

There is no duration imposed by law, but professional practice calls for a proposal to display a validity period, generally three months when nothing else has been agreed with the client. Past that deadline, the prices shown are no longer guaranteed, which protects the architect from a late signature based on a works cost or context that has since become outdated. In practice, it's worth stating that period explicitly on the proposal rather than leaving it implied, so no ambiguity remains about which terms apply at the moment of signature.

Going further

A compliant architect's fee proposal rests on three pillars that don't change from one project to the next: a billing method suited to the engagement, the complete legal mentions, and a clearly displayed validity period. Once this foundation is set in a reusable template, the only real variable from one project to the next is the content of the engagement itself — which is precisely what the architect's fee-proposal generator applies automatically, legal mentions and VAT calculation included, while leaving the decision on billing method and amount to the architect.

To go further on making a firm's administrative documents reliable, our comparison of the best AI tools for architects in 2026 covers other uses, from rendering to project management. For the next step — actually producing that fee proposal from a commission described in a few sentences — our guide to fee proposals with Claude covers the tool-side method.

Training 100% fundable through OPCO/FIFPL. Qualiopi-certified programme. To structure your administrative documents (proposals, invoices, site-meeting reports) with AI as part of our AI-driven practice management training, contact Educasium and specify your status (employee, freelancer, director) and your goal.