When a founder lets you into a round they could have filled twice over, they're not picking your money. Money is fungible - a pound from you spends exactly like a pound from the angel sitting next to you. What they're picking is you: your name on the cap table, the introductions you'll make, and how you'll behave the month the numbers go sideways.
That's the uncomfortable truth at the centre of finding good UK deals. The best rounds are competitive, and in a competitive round the founder is doing the choosing. So the more useful question for an angel isn't "what should I look for in a startup" - it's the one founders are asking about you.
Money is the table stakes. What gets you a seat is everything attached to it.
Do they bring credibility the round can use?
The first thing a founder weighs is what your name does to the round's signal. An angel who built and sold something in the same sector, or who carries a recognised operating reputation, makes the next conversation easier - with a lead investor, a first enterprise customer, a serious hire. That's worth more than the cheque, because it compounds.
Note the word relevant. A celebrated fintech angel adds little to a synthetic-biology seed round beyond cash. Founders can tell the difference between a name that opens doors in their world and a name that's simply famous. The credibility has to be the kind they can actually deploy.
Will the introductions be real?
Every angel promises to "open their network". Founders have learned to discount it heavily, because most of the time it evaporates the moment the money clears. The angels who stand out are specific before they invest: not "I know loads of people in retail", but "I'll introduce you to the buying director at two of the three grocers you're targeting, and I'll do it in the first fortnight".
A warm, well-framed introduction to one genuinely relevant person beats fifty LinkedIn connections. This is the heart of what people mean by "smart money", and it's mostly a promise until proven. Which is exactly why founders now check it - more on that below. If you want the fuller picture of the work itself, we covered what angel investors do beyond writing the cheque separately.
How fast do they decide - and do they say no cleanly?
Founders are running a process against the clock. Cash is finite, the round has momentum, and an angel who takes four weeks to reach a maybe is a drag on all of it. Speed reads as respect. A clear yes within a week or two, on terms the founder already understands, is genuinely valued.
So is a fast, clean no. Founders remember the angel who passed in two days with a straight reason far more warmly than the one who went quiet and let the question rot. The first keeps the relationship open for the next company. The second quietly burns it. If you need to do real due diligence, say so up front and give a date - founders can plan around honesty, not around silence.
What will they be like once the money's in?
This is the part founders care about most and ask about most privately. The nightmare angel writes a modest cheque and then behaves like a controlling board member: weekly update demands, opinions on every hire, special information rights nobody agreed to, a CC on emails that don't concern them. The prized angel does the opposite - shows up when asked, adds something when they do, and otherwise stays out of the way.
Restraint is a feature. The founder is running the company; a good angel acts like a useful resource on call, not a supervisor. Reputations on this travel fast, because founders talk to each other constantly. One war story about an exhausting investor and a door closes you'll never even see.
Are they easy to transact with?
Founders notice friction. An angel who tries to negotiate bespoke terms on a small cheque, won't sign the standard documents the round is using, or doesn't understand the mechanics they're operating under, costs the founder time they don't have. The smooth investor signs the same paper as everyone else and gets the money across quickly.
Tax fluency is part of this. Most UK seed rounds run on SEIS and EIS, and a founder values an angel who already knows how they work and won't slow things down with basic questions. To be clear about who benefits: the reliefs sit with the investor, not the company. Under SEIS, an investor can claim 50% income tax relief on up to £200,000 of investment in a tax year, with a minimum three-year holding period; under EIS it's 30% on up to £1,000,000 a year (or up to £2,000,000 where at least £1,000,000 goes into knowledge-intensive companies), again over three years. Companies need HMRC advance assurance before the round, and investors claim using the SEIS3 or EIS3 certificate the company issues. None of this costs the founder anything to grant - which is precisely why it's not a reason they'd pick one angel over another. It's table manners, not a differentiator. For the company-side eligibility rules, see which startups qualify.
How founders actually check all this
Here's what's changed. Founders no longer take the pitch on trust. Before they accept your cheque on a hot round, a growing number will quietly back-channel: they'll ask one or two founders you've already backed what you were actually like to have on the cap table. Were you responsive? Did the promised introductions land? Did you behave when things got hard?
Which means the way to be the angel founders want isn't to perform it in the pitch. It's to have been that angel for the last founder, so the reference call goes well without you in the room. Track record on conduct is becoming as legible as track record on returns - and arguably harder to fake.
The bottom line
Founders rank angels on a short, consistent list: relevant credibility, real and specific help, a fast and honest decision, and the discipline to be useful without being a burden. The cheque decides things only when capital is scarce. The rest of the time, the allocation goes to the person, not the pound. None of which tells you which company to back - that's your judgement, and your risk. What it tells you is how to be the kind of angel the best founders want to let in.