How to define your ICP when you sell a horizontal B2B product

By Dave Curran, Co-Founder, Firmbase | March 2026 | 10 min read

Every ICP framework you'll find online starts from the same assumption: you know what industry you sell to.

That works if your product is genuinely sector-specific. Payroll software for restaurants, compliance tools for financial services - if your ICP is clearly bounded by industry, defining it is mostly an exercise in being precise about which slice of that sector you want.

But what if you sell to everyone? An MSP sells IT services to any company with a network. A recruiter sells to any business that is hiring. A £10k SaaS product that solves a workflow problem sells to any company with that workflow, regardless of what they actually do. A business consultancy sells to any MD who is wrestling with the specific problem they solve.

For these sellers, the standard ICP frameworks fall apart. Sector-based filtering doesn't work when your best customers are spread across a dozen industries, and the advice to 'niche down' ignores the reality that the product genuinely does work for a very wide range of companies.

This article is for that seller. It covers what actually works when you're trying to define and map a horizontal ICP: the filters that matter, why the tools you're probably using are missing a significant chunk of your market, and how to build a complete picture of your target universe using UK public data.

What a horizontal ICP actually is (and why it needs a different approach)

An ICP - Ideal Customer Profile - is a description of the type of company most likely to buy from you, get value from what you sell, and retain or expand over time. The standard advice is to be as specific as possible: the more precise your ICP, the less time you waste on accounts that will never close.

That logic holds. The problem is that most ICP frameworks define 'specific' in terms of industry or sector, because that is the easiest filter to apply. Sector is a clean, categorical variable. You can filter by it in any CRM or prospecting tool without thinking.

For horizontal products, this approach fails for two reasons.

First, sector is genuinely not the defining characteristic of your best customers. A cloud infrastructure company's best customers are not 'all companies in the professional services sector.' They're companies at a particular stage of technical maturity, above a certain headcount in their engineering team, with a particular growth profile that signals increasing infrastructure complexity. Those companies exist across dozens of sectors.

Second, the tools available for sector-based filtering are significantly worse than most people assume.

The alternative is to define your ICP around the three variables that actually predict fit for a horizontal product: revenue band and trajectory, growth signals, and director or leadership profile. None of these require you to know what industry your customer operates in. All of them are available for every UK registered company.

The three filters that work for horizontal ICPs

Filter 1: Revenue band and trajectory

Every UK company that files accounts with Companies House gives you at minimum their net assets over time, and often their turnover. This is the starting point for any horizontal ICP, because it tells you two things that sector filtering cannot: whether this company has the budget to buy what you sell, and whether they are in a growth phase that creates the kind of problems your product solves.

A company with £2M in turnover that has been flat for four years is fundamentally different from one at the same revenue that has doubled its headcount and is filing new accounts every year showing a bigger cash position. The second company is going somewhere. They're hiring, investing, taking on new clients, building out processes. Those are the conditions under which companies buy new tools and services.

The specific band matters and varies by what you sell. A £10k SaaS product has a different sweet spot than a £50k consulting engagement. But the principle holds regardless: define your revenue floor, your revenue ceiling, and look for growth trajectory within that band.

What to look for in the data: Turnover or headcount growing year-on-year within your target revenue band. Consistent growth over two or three years is a more reliable signal than a single good year.

Filter 2: Growth signals

Beyond the filed accounts, there are real-time signals that tell you whether a company in your revenue band is currently in a growth phase - and therefore currently in a buying phase.

Director appointments are the most reliable. A company that has just hired a new Head of Operations, a first CFO, or a commercial director is signalling that they're building out their leadership structure. New leaders evaluate existing processes and tools in their first 90 days, making them more receptive to sales conversations than at almost any other point.

Recruitment patterns are the second most useful signal. What a company is hiring for tells you exactly what problem they're trying to solve. A company posting three SDR roles is scaling their sales function. A company hiring their first Finance Director is reaching an inflection point where financial complexity is increasing.

What to look for in the data: Leadership appointments in the last 90 days. Recruitment for roles that directly signal the problem your product solves.

Filter 3: Director and leadership profile

The third filter is the one most horizontal sellers underuse: who is actually running the company, and does that person match the profile of your best customers?

For a lot of horizontal B2B products, the best customers are founder-led or owner-managed businesses at a particular stage of professionalising - moving from informal processes to proper systems. The person running that company is often a managing director who has built something from scratch and is now wrestling with the complexity that comes from success.

You can see director tenure, previous appointments, and directorship history through Companies House.

Why SIC codes are the wrong tool for horizontal ICPs

Standard Industrial Classification (SIC) codes are the UK government's taxonomy for categorising business activity. For horizontal ICPs, they are almost useless.

The problem is not that SIC codes are inaccurate - it's that they were designed to classify economic activity for statistical purposes, not to identify sales prospects. The codes are broad, inconsistently self-assigned, and frequently out of date.

More importantly for horizontal sellers: your target market is by definition distributed across many SIC codes. A typical horizontal B2B ICP maps to between 8 and 14 SIC codes. Most filter-based prospecting tools miss between 30% and 60% of your actual target market as a result.

The companies you're missing aren't bad-fit accounts. They're companies that do exactly what your best customers do - they're just classified under a code you didn't think to include.

This is why natural language search matters so much for horizontal ICPs. Describing your ICP in plain English captures far more of your actual target market than any combination of SIC filters.

A worked example: building an ICP for a £10k SaaS product with no vertical focus

Imagine you sell a project management and client reporting tool for professional services firms. Your product is horizontal - it works equally well for a legal practice, a marketing agency, a management consultancy, or an IT services company.

Here's what a SIC-code-based approach gives you: a list of companies classified under professional services codes - probably 50,000 to 150,000 companies - with no way to distinguish the growing ones from the stagnant ones.

Here's what a signal-based approach gives you: companies in the relevant revenue band (say £1M to £8M in turnover) that have been growing consistently, that have made at least one director or senior hire in the last 12 months, and that do not yet have a Head of Operations or COO on the Companies House register, suggesting the coordination problem hasn't been addressed at leadership level yet.

That second list is dramatically smaller and dramatically better. Every company on it has the profile of a company in a buying window.

How Firmbase approaches this

Firmbase was built specifically for horizontal ICP mapping. You describe the kind of company you're looking for in plain English, and Firmbase searches across Companies House filings, job posting data, and funding round information to find UK companies that match.

The result is a continuously updated view of your ICP - not a list you pull once and let go stale - with the companies showing the strongest current signals surfaced at the top.

Start your free trial at app.firmbase.co/signup

Frequently asked questions

What is an ICP for a horizontal B2B product?

An ICP for a horizontal B2B product is a description of company characteristics that predict a good fit when you can't use industry or sector as a primary filter. The most useful ICP variables are financial (revenue band, growth trajectory), behavioural (hiring patterns, leadership appointments), and structural (company stage, director profile).

How do I find all the companies in my ICP in the UK?

The most complete way to map a horizontal ICP in the UK is to combine Companies House data with job posting signals and funding round information, and search across them using company profile criteria rather than sector filters.

What data should I use to define my ICP if I don't sell to a specific industry?

The three most predictive data points are: revenue band and trajectory (available from Companies House filed accounts), growth signals including director appointments and recruitment patterns (both publicly available), and company age relative to growth rate.

How many companies are in a typical UK B2B ICP?

A well-defined horizontal B2B ICP in the UK typically contains between 2,000 and 15,000 companies. A typical horizontal ICP maps to between 8 and 14 SIC codes, meaning filter-based approaches miss 30% to 60% of the actual addressable market.

Why are SIC codes unreliable for B2B prospecting?

SIC codes were designed for statistical classification, not sales prospecting. They are broad, frequently self-assigned without specialist guidance, and often out of date relative to a company's current activity.

How often should I update my ICP?

An ICP should be reviewed whenever you have meaningful new data about which customers have retained, expanded, or churned, and whenever your product evolves to serve a new or different buyer. In practice, most teams review quarterly.

About the author

Dave Curran is the co-founder of Firmbase, a UK B2B sales intelligence tool that helps sales teams find, prioritise, and reach the right accounts without needing a RevOps team to make it work. Before Firmbase, Dave co-founded Love Mondays (acquired by Glassdoor, where he went on to serve as VP of Product) and Openvolt.

Firmbase helps UK B2B sales teams discover their complete account universe, prioritise based on real buying signals, and reach out with genuine relevance - without the complexity of enterprise tools. Start your free trial