Fractional CTO or agency retainer: which do you need?

What a fractional CTO does

A fractional CTO works on your side of the table. Their job is to make technical decisions in the business's interest, write them down, and check that whoever builds the thing builds it properly.

In practice that means turning business goals into a technical plan and saying no to work that doesn't serve them. It means choosing platforms, tools and suppliers, and writing the brief they work to. It means owning the risks: security, data protection, backups, access, and what happens if a supplier disappears. It means reviewing code, tracking and integrations before they go live and before the invoice is paid. And it means keeping the website, CRM, finance system and reporting joined up rather than growing as separate projects.

What an agency does that a CTO should not

An agency has people, process and capacity, and that is what you pay for. Designers, developers and testers work in parallel. A repeatable process takes work from brief to launch. Specialists cover Shopify, paid media, SEO or design systems. And you can absorb a spike in work without hiring for it.

A CTO who spends all their time building is no longer doing the CTO job. An agency that sets its own brief and marks its own work has nobody checking it.

Signs you need one, the other, or both

You probably need a fractional CTO if you have several suppliers and nobody owns how their work fits together, if you keep paying for projects that are done but don't do what the business needed, or if you can't tell whether a technical quote is fair. The same goes if you are about to choose a platform, CRM or major supplier you can't cheaply undo, if an investor, lender or regulator is asking technical questions nobody can answer, or if your only technical person is about to leave.

You probably need an agency if you know what you need and it is clearly specified, if the work is mostly delivery such as a site, a campaign or a migration, if someone in the business can judge the result, and if you need more hands rather than more judgement.

Most growing businesses end up with both: a fractional CTO setting direction and checking quality, and one or more agencies doing the volume work. The CTO writes the brief, the agency builds, the CTO reviews. That split usually costs less than either alone would cost in mistakes, because nobody is marking their own homework.

What 19 days from first commit to launch required

We took a regulated SaaS platform from first commit to launch in 19 days.

Speed was not the point, and it wasn't the hard part. In regulated work, the hard part is deciding early what must be right on day one and what can safely wait. That is CTO work, not agency work. It meant writing down the requirements that could not slip, such as data handling, access control and audit records, before any code was written. It meant choosing hosting, sign-in and data storage that met those requirements without custom work, saying no to features that could wait for a second release, and reviewing every change against the written requirements before it went live.

An agency could have written the same code. Without someone making and recording those calls, it would have taken longer and been harder to defend to a regulator.

How fractional CTO pricing works in the UK

Fractional CTO fees are rarely published. Most providers sell days per month and quote privately. ITJobsWatch reported a UK CTO contract median of £635 a day for the six months to 29 October 2026, from a small sample of 12 adverts, and fractional CTO listings we checked in November 2026 typically showed £600 to £900 a day. At those rates, two days a month costs roughly £1,200 to £1,800, and four days £2,400 to £3,600.

Our Lead package covers fractional CTO or fractional marketing director work at £3,000 a month for two days, with message support between them and extra days at £1,200.

We run it the same way each time. The first month is about finding out: we review systems, suppliers, costs and risks and write down what we find in plain English. Then a written plan of what to fix, build and stop, in priority order with rough costs. After that, a monthly rhythm of planning, check-ins, hands-on work where it matters and a short report. We brief and review your agencies before you pay them. And when you are ready for a full-time CTO, we help you hire one and hand over everything we have documented.