Hourly billing makes one thing visible: time charged at an agreed rate. It does not show whether the work was necessary, efficient or valuable.
That limitation does not make hourly billing inherently wrong. Fixed price, retainers and outcome-linked fees create their own incentives and failure modes. The commercial model should allocate the risks each party can influence and make important trade-offs visible.
The source's strongest distinction is between cost transparency and value transparency. Keep it, without assuming every supplier responds mechanically to an incentive.
What time-based billing is good at
Time and materials can suit work whose scope cannot be known economically in advance, such as investigation, early discovery, incident response or advisory support.
The client can change direction without renegotiating every deliverable. The supplier does not need to price every uncertainty into a fixed fee. Time records can help forecast and explain where effort went.
It works well only with governance. Define the decision or objective, authorised roles and rates, budget or cap, reporting, priorities and review points. The client should see work completed, evidence learned and forecast to finish, not a timesheet alone.
A supplier can still be motivated to work efficiently by reputation, professional standards, opportunity cost, team capacity and the prospect of future work. Incentives are wider than the invoice formula.
Where the model creates risk
The supplier earns more revenue when more hours are approved. Reuse, automation or a smaller solution can reduce that revenue. Even with good conduct, utilisation targets and internal planning can influence behaviour.
The client carries much of the estimation risk. Ambiguous requirements, delayed decisions and technical surprises appear as additional cost. A low hourly rate can produce a higher total if the team takes longer or needs more supervision.
Time-based procurement can also encourage management of inputs. Meetings debate hours while the original outcome receives less attention.
Control those risks through option comparison, senior technical review, capped phases, backlog priority, forecast ranges and explicit approval thresholds. Ask the supplier to identify work it recommends removing.
Do not assume a custom integration proves misalignment simply because an off-the-shelf connector later appeared cheaper. Security, licence, fit, support and timing may differ. The original case requires records before that conclusion can be published.
Fixed price changes the incentive
A fixed-price supplier can improve margin through efficient delivery. It can also reduce quality, resist useful change or interpret ambiguity narrowly.
Fixed price is strongest when acceptance is clear, dependencies are understood and the supplier controls enough of delivery. The price should state assumptions, exclusions, client responsibilities, change process and quality criteria.
Contingency is not automatically “the supplier's problem”. The client pays for risk through the price and may pay again when an excluded assumption changes. Competitive bidding can suppress visible contingency and produce later disputes.
Use fixed phases where uncertainty can be bounded. A short discovery, prototype or technical assessment may allow a credible delivery price without pretending the whole programme was knowable on day one.
Outcome-linked fees need attribution and control
Linking part of a fee to an outcome can align attention. It can also reward gaming, neglect of unmeasured quality or action outside the client's interests.
Define the metric, baseline, source, period, exclusions and calculation. Identify variables controlled by the client, supplier and market. Set safeguards for accessibility, security, client quality and long-term effect.
A conversion target may be influenced by pricing, media, sales response and seasonality beyond the digital partner. A shared bonus or risk band may be fairer than making the entire fee contingent.
Avoid outcome fees in situations where the supplier could influence a regulated, vulnerable or high-consequence decision inappropriately. Legal and procurement review should examine the incentive, not only the wording.
The source's SaaS outcome case and uplift need contract, analytics and client permission before publication.
Retainers can create continuity or complacency
A retainer provides access to capability and supports a changing portfolio. Objectives and capacity can be reviewed without a new procurement event for every task.
It can deteriorate into prepaid hours, vague availability or a list of activity with no portfolio choice. Define service boundaries, outcomes, planning rhythm, response expectations, unused capacity treatment and exit.
A retainer does not need to be “earned” only after a prior project, though evidence of fit reduces risk. A well-scoped first engagement can reasonably use one where ongoing demand is clear.
Review whether the relationship is learning and whether the retained team remains appropriate.
Capacity-based teams are another option
A client may fund a stable multidisciplinary team or amount of capacity for a period, then prioritise work within it.
This gives flexibility and preserves team knowledge. Cost is predictable while output varies with priority and complexity. The client needs a capable product owner and timely decisions.
Measure throughput, quality, outcomes and learning without pressuring teams to maximise tickets. Clarify which specialist support sits outside the capacity and how people are substituted.
This model can be a more transparent version of a retainer and still needs an explicit portfolio.
Select the model across five dimensions
Uncertainty
How much will be learned through the work? Who can reduce that uncertainty and at what cost?
Acceptance
Can both sides describe a completed result and quality level? Are external dependencies material?
Outcome influence
Can the supplier materially affect the result, and can contribution be measured fairly?
Change frequency
Will priorities move as evidence emerges? How expensive is contractual change?
Relationship and capability
Does the client have ownership and decision capacity? Does the supplier have evidence of delivery and transparent costing?
Risk tolerance and procurement constraints also matter. A hybrid often fits: capped time-based discovery, fixed implementation of stable scope, then an objective-led capacity arrangement.
Price is only one control
Whatever the model, require:
- a clear objective and success conditions;
- scope or backlog and current priority;
- roles and decision rights;
- assumptions and dependencies;
- quality, security and accessibility requirements;
- budget, forecast and change thresholds;
- evidence of progress and value;
- records of decisions;
- termination, handover and intellectual-property terms.
Compare total expected cost and plausible variation, rather than rates alone. A senior person at a higher rate can be better value; a fixed fee can be expensive if it includes risk the client could remove.
Open-book costing can improve understanding and does not resolve weak scope or governance.
The client influences commercial performance
Late access, inconsistent feedback and unavailable decision-makers consume capacity under every model. Time billing displays the cost; fixed price turns it into a change or margin dispute; a retainer displaces other work.
Client responsibilities should be specific and achievable. Suppliers should surface the effect early instead of accumulating a claim. Both parties need a route to pause when a dependency fails.
Shared accountability does not remove the supplier's duty to estimate, advise and manage competently.
Questions to ask a prospective partner
Ask why this model fits the particular work and which alternative was rejected. Request a cost range, important assumptions and a scenario in which the model would change.
Ask how the supplier benefits from efficiency and how the client benefits. Examine reuse, third-party products and intellectual property.
Ask how value and quality will be reviewed. A supplier should be able to describe when it would recommend stopping or reducing work.
Finally, ask for a redacted example of forecast change and how it was handled. The mechanics matter more than a statement about partnership.
Choose deliberately
The source cited 25 years, more than 170 projects and multiple client costs. Those details need current internal verification.
Hourly billing can reward more time and can also buy appropriate flexibility. Fixed price can reward efficiency and can also reward minimum compliance. Outcome fees can align value and can also distort it. Retainers can build continuity and can also hide inactivity.
The right choice exposes the risk the parties need to manage and gives each a reason to make good decisions.
We've put together a one-page commercial model assessment guide that maps the three main models against the key decision factors - scope definition, outcome measurability, relationship maturity, and risk tolerance. It's designed to be something you can share with your finance director or legal team before structuring the engagement. Download the commercial model assessment guide below.
