Ask a new angel how they sized their last cheque and you'll usually hear a number that came from the deal: the round had a £10,000 minimum, so they put in £10,000. Ask someone who has built a portfolio over a decade and the answer runs the other way. They started from the total they were willing to lose, worked out how many companies that total had to cover, kept a chunk back for later, and only then arrived at a per-deal figure. Same decision, opposite direction of travel - and the second version is the one that survives contact with a power-law market.
So the honest framing isn't "how much should I put into this company?" It's "what does each cheque need to be for the whole programme to make sense?" Three things set that: your total budget, how widely you want to spread it, and how much you keep in reserve. The tax reliefs then quietly adjust the net cost of whatever you land on.
Why angels size from the top down
Early-stage returns don't average out. Most startups return little or nothing, and a small handful return almost everything - the power law that governs the asset class. You can't reliably tell at the seed stage which of your bets is the rare winner, so the sane response is to make sure you've made enough bets to own one if it appears. That's the instinct behind top-down sizing.
In practice it's a short sum. Take the total you're prepared to commit over, say, three to five years - money you can genuinely afford to lock away and lose. Decide roughly how many companies you want that total to touch. Divide. The result is a rough per-company budget, and the cheque you write into any single deal is a fraction of that, not the whole thing. An angel with a £100,000 programme aiming at twenty companies is working with about £5,000 a company - which, as we'll see, is rarely the same as a £5,000 first cheque.
The cheque isn't the starting point. It's what falls out once the portfolio maths is done.
How diversification sets the floor
The number of companies you target is doing a lot of quiet work in that sum. Spread too thin and each position is too small to bother with, or you simply run out of good deals. Concentrate too hard and a single failure - which, statistically, is the base case - takes a disproportionate bite. Commentators on early-stage investing often talk about portfolios built towards ten, twenty, or more holdings over several years, precisely to give the power law room to work. The right figure for you depends on your circumstances and is a question for you and an adviser, not something we'd prescribe.
The route you choose then sets the practical floor on each cheque. Go direct - founder to your bank account, your name on the cap table - and rounds tend to be built around larger commitments, commonly £5,000 to £25,000 or more, because founders would rather manage a few sizeable backers than forty small ones. Go through a syndicate or an online platform, where a lead negotiates and many angels pool in behind a nominee, and per-deal minimums frequently start around £1,000 to £5,000. That lower floor is the whole reason the pooled route exists for newer angels: the same budget reaches far more companies.
Why reserves matter as much as the first cheque
Here's the part beginners almost always miss. The first cheque is rarely the last one a company asks you for. The good ones raise again - a bridge, a Series A - and those later rounds are where an angel can put more money behind a bet that's actually working, often at a higher price but with far more evidence. Spend your entire per-company budget at first cheque and you've no powder left for exactly the moment when adding to a winner does the most for your returns.
That's what reserves are: money deliberately held back from a company's allocation to deploy in its later rounds. There's no universal split, but it's common to see angels reserve a meaningful share - sometimes as much as they put in initially - for follow-ons. Return to our £5,000-a-company angel: that might mean a £2,500 first cheque and £2,500 kept in reserve, or a smaller initial position with more powder behind it. The choice of whether and how to follow on is its own discipline, covered in our piece on pro-rata rights and follow-on investing.
Reserves are also why uniform first cheques are popular. If you can't pick winners early, the argument runs, don't try to at the point of entry - write the same modest cheque into everything and concentrate later through follow-ons. Others vary the initial cheque by conviction. Both are common, and neither is the "right" one; the point is that the decision is deliberate, not set by whatever the round's minimum happened to be.
How SEIS and EIS resize the net cheque
For UK taxpayers, the government's venture capital schemes change the arithmetic in a way that's easy to underrate. They don't make a cheque safer, but they do change what a given cheque costs you out of pocket - which means the same personal budget can sit behind a larger gross investment.
SEIS, the Seed Enterprise Investment Scheme, targets the youngest companies and carries the heaviest reliefs: 50% income tax relief on up to £200,000 of investment per tax year, provided you hold the shares at least three years. On a qualifying £10,000 SEIS cheque, that's up to £5,000 back against your income tax bill - so the net cost before any other relief is £5,000. Gains on the shares are exempt from capital gains tax if held three years with the relief received; there's CGT reinvestment relief equal to 50% of a gain reinvested into SEIS shares, on up to £100,000 of investment a year; loss relief applies if the company fails; and relief can be carried back to the previous tax year.
EIS, the Enterprise Investment Scheme, covers slightly larger early-stage companies and gives 30% income tax relief on up to £1,000,000 per tax year - or up to £2,000,000 if at least £1,000,000 goes into knowledge-intensive companies - again with a three-year minimum hold. Gains are exempt if held three years with relief, there's CGT deferral relief, loss relief, and the same carry-back option. The company-side limits matter too if you're checking a deal qualifies: as of HMRC guidance updated for April 2026, a standard company must have gross assets no greater than £30 million before the share issue, can raise up to £10 million in a 12-month period, and faces a £24 million lifetime cap, generally within seven years of its first commercial sale, with higher ceilings for knowledge-intensive firms. These figures move, so confirm the current detail on gov.uk's Enterprise Investment Scheme guidance.
The mechanics catch people out, so two reminders. The reliefs depend on the company qualifying and on HMRC's process: companies usually obtain advance assurance before the round, and after you invest they issue an SEIS3 or EIS3 certificate - that's what you use to claim. And the reliefs are worthless without UK income tax to set them against, so you generally need to be a UK taxpayer to benefit. For context on the wider schemes, see our explainers on how SEIS 50% relief works and how EIS 30% relief works.
Putting the number together
Stack the pieces and a workable method appears - though not a single magic figure, because anyone who hands you one of those is guessing on your behalf. Start with the total you can afford to lose over several years. Pick how many companies you want it to reach. Divide for a per-company budget, then split that budget between a first cheque and a reserve for follow-ons. Check the route's minimum will let you in at that size, and let SEIS or EIS tell you what the net cost actually is once relief is claimed.
Do it in that order and the per-deal cheque stops being the anxious question and becomes the obvious answer. The discipline isn't in being clever about any one company. It's in refusing to let a single round's minimum decide how you spread - and risk - the whole pot.
This article is general information and editorial analysis, not financial or investment advice. The Carry is independent of any fund, syndicate, or platform. Tax treatment depends on your individual circumstances and the rules can change. Speak to an FCA-regulated adviser before making any investment decision.
Frequently asked questions
How do angels decide how big a cheque to write?
Most angels start from the total they're prepared to commit over several years, divide it across the number of companies they want to back, then hold some of that total in reserve for follow-on rounds. The single cheque is the output of that sum, not the starting point. The per-deal figure is then constrained by the round's minimum and the route used to invest.
What is a typical angel cheque size in the UK?
It varies widely by route. Direct cheques into a single startup commonly run from £5,000 to £25,000 or more. Through a syndicate or an online platform, per-deal minimums often start around £1,000 to £5,000, which lets the same budget cover more companies. There's no legal minimum or maximum, only the limits the round and the scheme rules impose.
What are follow-on reserves and why do they matter?
Reserves are money an angel deliberately keeps back to invest again in the companies that are doing well, usually in a later round. Because early-stage returns concentrate in a few winners, the ability to put more into those winners can matter as much as the initial cheque. Many investors reserve a meaningful share of a company's total budget for this rather than spending it all up front.
How do SEIS and EIS change the size of a cheque?
For UK taxpayers backing qualifying companies, SEIS gives 50% income tax relief and EIS gives 30%, claimed once you receive an SEIS3 or EIS3 certificate and hold the shares at least three years. That lowers the net cost of a given cheque, so the same out-of-pocket budget can fund a larger gross investment. The reliefs change the maths but not the risk.
Should every cheque be the same size?
Not necessarily. Some angels write uniform cheques for simplicity and to avoid over-weighting any single bet at the point of entry, since it's hard to pick winners early. Others vary the size by conviction. Both are common. This is general information about how investors approach the decision, not a recommendation of any particular method.