Output-based vs Time & Material: why we killed T&M at Abbeal.

The structural problem with T&M

Time & Material has been the typical contract for French consulting firms since the 1990s. The client pays a TJM (average daily rate) per engineer multiplied by booked days. Simple, predictable billing, contractually light. Except it creates three structural pathologies.

Pathology 1 — Wrong incentive on quality

A firm billing on T&M earns more if the project lasts longer. An engineer finishing a task in 3 days instead of 5 deprives their employer of 2 billing days. Nobody says this out loud, but it's math. Pressure to fill billable hours is constant. At low-cost firms, this translates to junior staffing hidden behind senior CVs. At high-end firms, it's subtler: over-engineering, unrequested refactors, over-documentation. Premium code is also code that takes 3× longer to write.

Pathology 2 — Friction at scoping

When the client asks « can we also add X? », the T&M answer is « yes, 4 extra days ». The client negotiates or caves. Neither stops to ask if X is really useful. T&M strips scoping of its economic logic.

Pathology 3 — No business alignment

The client wants a product that works in production, backed by business metrics (conversion, retention, MRR). The T&M firm wants billed days backed by activity metrics (tickets closed, PRs merged). The two stack but don't align. The client's commercial success is neutral for the firm.

What is Output-based exactly

Output-based (sometimes called Fixed Price or Outcome-based, with some nuances) consists of billing a deliverable rather than time. Three common variants:

1. Sprint forfait

The client pays a fixed forfait for a 2-week sprint, with scope defined upfront (3-5 priority user stories). Abbeal commits on production-ready delivery, code reviewed, tested and deployed. If the team finishes in 6 days instead of 10, they use the rest to ship tech debt or extras.

2. Feature forfait

The client pays a fixed forfait for a complete feature (e.g. Stripe checkout integration), with an accepted scoped spec. Abbeal delivers or refunds. Our preferred format for 2-6 week missions.

3. Outcome-based (forfait + bonus)

The client pays a minimum forfait covering costs, plus a bonus if a target business metric is hit (e.g. +€X if checkout conversion goes from 2.1% to 3.5% in 90 days). The most demanding format, also the one that aligns most.

Abbeal's 2022-2026 shift: the numbers

In 2022, 100% of Abbeal missions were T&M. That was the French consulting market legacy. Mid-2022, we kicked off 3 pilot missions on Output-based sprint forfait. The results surprised us:

• Team shipped faster (-20% days on average for same scope, measured post-mortem)
• Engineers were more engaged (internal sentiment +18%)
• Clients were more satisfied (NPS +30 points on those 3 missions)

In 2023, we moved 30% of portfolio to Output-based. In 2024, 55%. In Q2 2026, we're at 78% of revenue on Output-based.

Aggregate metrics across 12 Output-based missions vs 12 T&M missions (all 2024-2025, comparable contexts):

• **Abbeal gross margin**: T&M 28% → Output-based 46% (**+18 pts**)
• **Average client NPS**: T&M 41 → Output-based 65 (**+24 pts**)
• **Average mission length**: T&M 8 months → Output-based 14 months (**×1.7**)
• **Contract re-sign rate**: T&M 52% → Output-based 87% (**+35 pts**)
• **Engineer velocity (story points/sprint)**: T&M base 100 → Output-based 124 (**+24%**)

How we operate Output-based concretely

Week 0 — Scoping & Pre-mortem

Before signature, 5 days of paid scoping (fixed forfait, credited to the main contract). The Abbeal team that will operate the mission audits the code, reads specs, runs 2-3 sessions with the client PM. Output: a precise backlog for the first 3 sprints, with acceptance criteria and identified risks.

Sprints 1-N — Forfait delivery

Each sprint, scope locked at sprint start (Sprint Planning Monday). Fixed forfait paid at sprint start. If Abbeal underdelivers (= incomplete scope at sprint review), we extend for free until completion. If we overdeliver, we keep the margin.

Structured Change Request

If the client wants to modify scope mid-sprint, it's a formal Change Request: we quantify impact, document, sign. No « can you just add this quickly ». This discipline is non-negotiable and what makes the model economically viable.

Retro-Pricing at mission end

Every 6 months, we review pricing with the client: if the team over-delivered (= more scope at same forfait), we adjust up for the next semester. If under-delivered (= delays), we adjust down. This transparency avoids surprises and nurtures the long relationship.

The 3 success conditions

Condition 1 — Team seniority

A junior team CANNOT do Output-based cleanly. They overestimate capability, underestimate bugs, end up shipping mediocre code to meet the forfait. At Abbeal, the model only runs because all engineers have >5 years XP on the stack. Seniority enables accurate estimation.

Condition 2 — Rigorous upfront scoping

Scoping is the critical step. Sign a forfait on fuzzy scope, you'll blow up economically. At Abbeal, we refuse to sign a forfait before 3-5 days of paid scoping. The client who wants to just start in T&M and switch to forfait later when we know better is a bad signal. We insist on initial scoping or keep T&M (rare cases).

Condition 3 — Change Request discipline

Client and us must have the Change Request reflex when scope moves. That means: financial transparency, scope traceability, no silent scope creep. Culturally more demanding than T&M where everything is negotiable. But that's what makes the model last 14 months instead of 8.

Who it works for, who not

**Output-based works when**:

• Scope is framable (= defined product, not exploratory POC)
• Abbeal team is >3 engineers (risk mutualisation works less in solo)
• Mission is >3 months (initial scoping amortises over duration)
• Client has a mature PM or Product Owner on their side (scope doesn't change every 3 days)

**T&M remains relevant when**:

• POCs or product-market exploration phases (rewrites expected)
• Mission < 2 months or ad-hoc intervention (scoping overhead not amortisable)
• Client without mature PM wanting an outsourced internal-team draft
• Absolute urgency where contract must start in 48h

On Abbeal portfolio Q2 2026: 78% Output-based, 22% T&M (essentially early-stage POCs and short technical assistance).

Buyer resistance

All Big 4, Sopra Steria, Capgemini, etc. procurement is trained on T&M. When a buyer receives an Abbeal Output-based quote, the first reaction is « it doesn't fit our PO templates ».

Our standard response:

• We can formulate the forfait as a T&M equivalent (days × TJM) to fit the PO, with an annex clause for transformation to fixed forfait.
• The forfait includes free overrun until completion. That's a buyer advantage, not a risk.
• Change-request traceability replaces detailed T&M line items.

On 12 Output-based missions started 2024-2025, we got the format past 11 buyers out of 12. The 12th refused for strict internal policy. We did T&M on that mission, and we do worse on it.

How to start

If you operate a consulting firm or you're client-side wanting to explore Output-based, here's the starter pack:

1. Identify ONE pilot mission, 3 months max, with clear scope
2. Price as fixed forfait (estimate T&M, add 10% buffer, formulate as forfait)
3. Invest 3-5 days of upfront scoping (massive ROI)
4. Measure across 3 sprints the deltas vs T&M baseline
5. Decide to expand or not

At Abbeal, we also help competing consulting firms make this shift against a retro-commission. The Output-based methodology is not our defensive secret — it's more efficient for the market that everyone knows it.