Non-technical founders usually ask "who should build my product?" when the better first question is "who should make my technical decisions?" A development agency builds. A fractional CTO decides and checks. A technical co-founder does both and takes equity for it. Mixing those roles up is how founders end up with an agency approving its own work, or a co-founder who owns 30% of a company they left after eight months.
This guide compares the three options, plus a first senior hire, on cost, ownership and risk, and gives a decision by funding stage. It is written for founders in the UK, US and elsewhere who are about to spend their first serious money on software. It does not cover equity law or how to split founder shares, and it is not a recruitment guide for full-time CTOs.
What is a fractional CTO?
A fractional CTO is a senior technology leader who works part-time, often one to three days a week or on a retainer, owning technical strategy, architecture, vendor oversight, security and early hiring. They give a startup CTO-level judgment without a full-time salary or co-founder equity, and usually do not write most of the code.
The four options side by side
| Option | What you get | How you pay | Main risk |
|---|---|---|---|
| Fractional CTO | Decisions, architecture, vendor oversight, hiring plan | Day rate or monthly retainer, sometimes small advisory equity | Too little time to catch problems; conflicts if they earn referral fees |
| Development agency | A delivery team that designs, builds, tests and ships | Fixed price per phase, or time and materials | Nobody independent checks the agency's decisions |
| Technical co-founder | Long-term ownership of the technology and the team | Significant equity, usually vesting over years | Hard and expensive to unwind if the fit is wrong |
| First senior engineer hire | Full-time building capacity and in-house knowledge | Salary, employer taxes, benefits, recruitment | A strong builder is not automatically a good technical leader |
What does a fractional CTO cost?
There is no reliable public index of fractional CTO pricing, so be wary of anyone quoting a precise "market rate". The useful benchmark is the full-time equivalent. The median advertised salary for a chief technology officer in the UK was £100,000 in the six months to 17 September 2026 (ITJobsWatch). Two days a week is 40% of that role, about £40,000 a year in salary terms before employer taxes, benefits and recruitment, which a fractional arrangement avoids.
Fractional leaders typically price above the pro-rata salary figure because they carry their own gaps between clients, insurance and business costs. Apply the same pro-rata check to local salary data if you are hiring in the US or elsewhere. What matters more than the headline rate is what the time buys:
- Which decisions they own and which they only advise on.
- How many hours a month are committed, and what happens in a crisis week.
- Whether code review, security review and vendor meetings are included.
- Notice period and handover obligations when they leave.
Who should you hire at each stage?
| Stage | Usually the right first move | Why |
|---|---|---|
| Idea, no funding | A few paid hours with a fractional CTO or independent adviser, then a no-code prototype or a discovery phase | You need a scope and a sanity check, not a team |
| Pre-seed with a build budget | Agency for the first release, with independent technical review at key milestones | Fastest route to a working product without payroll commitments |
| Seed, product in market | Fractional CTO plus agency, starting to hire a first senior engineer | Someone must own architecture and hiring while delivery continues |
| Series A and beyond | Full-time CTO or VP Engineering with an in-house team, agency for specific workstreams | Technology is now a permanent capability and investors expect a leader |
| Technology is the product (deep tech, AI research, infrastructure) | Technical co-founder from the start | The core advantage cannot be outsourced or rented part-time |
Our longer comparison of agency vs in-house development teams covers the transition from external delivery to your own engineers, and MVP vs full product covers what to build first.
The conflict of interest nobody mentions
An agency that offers its own "CTO" to a client is offering someone who will approve the agency's architecture, estimates and invoices. That person may be excellent. They are still not independent. For a small first release the trade-off is usually acceptable. Once the budget is large, or investors will scrutinise the codebase, separate the builder from the reviewer.
The same applies in reverse. A fractional CTO who receives referral fees from the agencies they recommend has a financial interest in the choice. Ask directly and get the answer in writing. A good fractional CTO will disclose it without being asked.
Fractional CTO plus agency: who owns what
The combination works well when the split is explicit. This is the division we recommend to clients who bring their own technical adviser.
| Responsibility | Fractional CTO | Agency |
|---|---|---|
| Product and technology strategy | Owns | Advises |
| Architecture decisions | Approves | Proposes and documents |
| Estimates and sprint plans | Challenges | Owns |
| Day-to-day delivery and code | Spot-checks through review | Owns |
| Security and compliance posture | Sets the standard | Implements and evidences |
| Hiring the in-house team | Owns | Supports handover |
| Vendor and contract review | Owns | Not involved |
How to hire a fractional CTO
- Write down the decisions you need made in the next six months: stack, vendor, security, first hires, AI strategy. Hire for those, not for a title.
- Ask for evidence of shipped products at a similar stage, and speak to at least two founders they worked with.
- Test judgment with your real problem. Give them your brief or an agency quote and ask what they would change. You will learn more in an hour than from a CV.
- Agree scope, hours and availability in writing, including response times when something breaks.
- Ask about conflicts: referral fees, equity in suppliers, other clients in your market.
- Make sure they will hand over: documented decisions, access lists, and a plan for replacing themselves with a full-time leader.
If you already have a delivery partner and want an outside view of the code, a structured review like our technical due diligence checklist is a good first engagement for a fractional CTO.
Red flags in each option
- Fractional CTO: no recent hands-on work, vague availability, reluctance to disclose other clients or referral arrangements.
- Agency: no access to the code repository from day one, estimates without assumptions, a "CTO" who has never reviewed another team's work.
- Technical co-founder: equity with no vesting, unwillingness to commit full time, or someone chosen mainly because they are available.
- First hire: hiring a senior developer and expecting them to also set strategy, run vendors and recruit.
Frequently asked questions
What does a fractional CTO do?
A fractional CTO owns technology decisions on a part-time basis: architecture, stack, security standards, vendor selection and oversight, technical hiring and the technology roadmap. They represent technology to investors and the board. Most do some code or architecture review but do not build the product themselves; that is usually an agency's or in-house team's job.
How much does a fractional CTO cost?
There is no reliable public price index. A practical benchmark is the pro-rata cost of a full-time CTO: the UK median CTO salary was £100,000 in September 2026, so two days a week equates to about £40,000 a year in salary terms. Fractional leaders usually charge somewhat above pro-rata because they carry their own business costs, but you avoid employer taxes, benefits and recruitment fees.
Should I hire a fractional CTO or a development agency first?
If you do not yet have a clear scope or cannot judge technical proposals, a few paid hours from a fractional CTO or independent adviser first will save money. If you already have a clear scope and budget, start with an agency for delivery and bring in independent review at key milestones. Most seed-stage companies benefit from both.
Can a development agency act as my CTO?
An agency can provide technical leadership, and for a small first release that can be fine. It is not independent, because the same people propose, build and approve the work. Once budgets grow or investors will review the code, keep a separate person responsible for technical decisions and oversight.
When should I hire a full-time CTO?
Usually once technology is a permanent in-house capability: you are hiring engineers, the product is in market, and investors expect a technical leader, often around Series A. Hire a technical co-founder from day one if the technology itself is your core advantage, such as deep tech or AI research.
Key takeaways
- An agency builds, a fractional CTO decides and checks, and a technical co-founder does both in exchange for equity.
- Benchmark fractional CTO pricing against pro-rata full-time salary; the UK median CTO salary was £100,000 in September 2026.
- An agency's own CTO is not independent; separate builder and reviewer once budgets or investor scrutiny grow.
- Pre-seed founders usually do best with an agency plus milestone reviews; seed-stage companies with both a fractional CTO and a delivery team.
- Put ownership of decisions, hours, conflicts and handover in writing whoever you hire.
Bring your adviser, or ask us for a straight answer
We are a development company, so we will not pretend to be your independent CTO. What we will do is work openly with the adviser you choose, document every architecture decision for their review, and give you repository access from the first day. If you do not have an adviser yet, send us your brief and we will tell you honestly whether you need one before you need a build team. UK clients contract with our UK company and can call our London office on +44 7863 374791 to arrange a video call. See our product engineering service for how we run discovery.