Fractional CTO vs Development Agency: Which Do You Actually Need?

The distinction is simpler than the marketing around it suggests.

An agency builds to a specification. Give them a clear brief and they will deliver against it competently.

A fractional CTO writes the specification and is accountable for whether it was the right one.

Almost every expensive mistake in this area comes from hiring the first when the real problem was the second.

The failure mode

It goes like this. A non-technical founder has a clear product vision. They hire an agency, who ask sensible questions and get sensible answers. The agency builds exactly what was described, on time, to a decent standard. Everyone behaves professionally throughout.

Six months later the product exists and is not working — not because the code is bad, but because of decisions nobody in the room was equipped to make. The data model reflects how the founder described the business rather than how it actually operates. An integration that turned out to be central was scoped as an afterthought. The architecture cannot support the pricing model the business has since moved to.

The agency did their job. The specification was wrong, and no one involved had the remit to say so.

What a fractional CTO actually does

Not writing code, mostly. The role is decision-making and accountability:

• Architecture and stack. What to build on, what to buy rather than build, and which choices are cheap to reverse later versus which lock you in for years.
• Vendor and hire selection. Writing the technical brief, assessing proposals, and telling you which quote is realistic and which is fiction.
• Oversight. Reviewing what contractors actually ship against what they said they would.
• Due diligence. Preparing your codebase for investor scrutiny — or reviewing the other side when you are acquiring or depending on someone.
• Sequencing. Ordering the roadmap so the thing you need to prove next is provable, rather than blocked behind six months of foundations.
• Budget. What technology should cost at your stage, and what to stop paying for.

What each costs in the UK

• Fractional CTO: typically £450 to £1,400 per day. A common two-day-a-week arrangement lands around £7,000 to £11,000 a month. Fixed retainers buy less time for less money rather than a lower day rate — ours is £4,500 a month for roughly four days, which is about £1,125 a day.
• Development agency: £25,000 to £150,000 for an initial build, or £8,000 to £30,000 from a fixed-price specialist.
• Full-time CTO: £120,000+ salary, plus equity, employer national insurance and recruitment fees. Realistically £160,000+ all-in, with a hiring process measured in months.

A short decision guide

Hire an agency if

• You know precisely what to build and why.
• Someone on your side can evaluate whether the work is any good.
• The scope is well bounded and unlikely to shift underneath you.

Hire a fractional CTO if

• You are non-technical and making decisions you cannot properly assess.
• You already have developers or an agency and no way to judge their output.
• An investor has asked for technical due diligence and you do not know what they will find.
• You have inherited a codebase and need to know whether to fix or replace it.

You probably need both if

You are non-technical, you need something built, and the thing being built is the business rather than a side project. This is the most common situation and the one most poorly served by treating the two as alternatives.

On buying both from one supplier

The obvious objection: if the same firm sets the direction and gets paid to build it, the incentive points one way.

That is a real conflict and worth naming rather than glossing over. The counterweight is that separating them has its own failure mode — the advisor who is never accountable for whether their architecture actually worked, because someone else was holding it by the time it mattered.

Our position, for what it is worth: we quote leadership and delivery separately, so you are never paying retainer rates for implementation hours, and the retainer does not require that we do the build. If the honest answer is that your existing developers should do it, that is the answer you get. It is a structure that makes the conflict visible rather than eliminating it, and you should weigh it accordingly.

Details on the fractional CTO page, or if the specification is already clear and you just need it built well, the MVP development page.