Calla Health
Priya Menon
SEIS
AI triage for NHS mental health waiting lists
68% raised214 backers · £150k
UK SEIS/EIS eligible raises · Now open
Back founders
before
they're obvious.
ProbablyBig is a UK platform where you discover early-stage founders, build conviction, and back raises from smaller amounts — with SEIS/EIS tax relief built in.
Early-stage investing is high risk. You could lose all the money you invest and you may not be able to sell your shares for a long time.
£2.1Mbacked this month
1,400+active backers
SEIS/EISguidance included
Live raises
Meet the founders
These raises are live now. Each founder has passed our review and holds SEIS or EIS Advance Assurance where indicated.
Calla Health
Priya Menon · CEO & Co-founder
SEIS
AI triage for NHS mental health waiting lists
£102k of £150k68%
214 backers
12d left
Fast
From £100
Stackr
Tom Ridley · Founder
EIS
Revenue-based finance for UK SMEs
£164k of £200k82%
389 backers
5d left
Very Fast
From £250
Verdant
Amara Osei · CEO
SEIS
Carbon tracking for supply chains
£45k of £100k45%
97 backers
21d left
Building
From £100
Tutor Loop
Bea Zhang · Founder & CEO
SEIS
Adaptive tutoring that learns how each child learns
£46.5k of £150k31%
121 backers
28d left
Building
From £100
Halo Materials
Dr. James Okafor · CTO & Co-founder
SEIS
Self-healing polymers from agricultural waste
£28.5k of £150k19%
44 backers
35d left
Early
From £100
Flint
Layla Hassan · Co-founder
EIS
On-demand tradespeople, rated and insured
£91.5k of £150k61%
278 backers
9d left
Fast
From £250
This is early-stage investing. You could lose all the money you invest and you may not be able to sell your shares for a long time. Tax treatment depends on your personal circumstances. ProbablyBig does not provide investment advice.
How it works
From discovery to cap table in minutes
ProbablyBig makes early-stage investing feel human. The regulated infrastructure runs in the background — you just back founders you believe in.
01
Discover founders
Browse live raises from vetted UK founders across every sector. Watch founder videos, read the pitch, and follow the raise for updates.
02
Build conviction
Read the investment documents, see the traction, and ask the team questions. We surface SEIS/EIS status and risks upfront — no small print surprises.
03
Back the founder
Invest from smaller amounts in minutes. Complete appropriateness checks, sign documents, and transfer funds securely. Cooling-off period included.
04
Follow the journey
Join the cap table and receive founder updates, documents, and milestones directly in your portfolio. SEIS/EIS certificates when available.
Tax relief
SEIS/EIS can reduce your effective risk — not eliminate it
The UK government's Seed Enterprise Investment Scheme and Enterprise Investment Scheme offer income tax relief on qualifying investments. Where a raise holds Advance Assurance, eligible investors may be able to claim this relief.
SEIS
50%
income tax relief
Up to £200k raised per company
EIS
30%
income tax relief
Up to £5M raised per year
Tax treatment depends on your personal circumstances and the company maintaining qualifying status. This is not tax advice. Always consult a qualified adviser.
Example — SEIS eligible investment
You invest£2,000
SEIS income tax relief (50%)− £1,000
CGT exemption on gainsTax-free
Effective exposure (if eligible)£1,000
If the company succeeds and shares are held for the required period, any gains on the SEIS portion may be free from Capital Gains Tax. If the company fails, Loss Relief may further reduce your net loss. This example assumes full income tax relief eligibility.
For founders
Raise from the people who believe before the market catches up
ProbablyBig helps early founders turn their story, traction, and community into a compliant public raise — with lower fees and SEIS/EIS guidance built in. No upfront cost. No VC gatekeeping.
5%Success fee only
£0Upfront cost
1.5%Investor fee
FreeSEIS/EIS guidance
- 5% success fee — undercutting every competitor
- No upfront listing cost
- SEIS/EIS Advance Assurance guidance built in
- Bring your community into the raise
- Compliance review and financial promotion sign-off
- Founder updates and investor Q&A tools post-raise
Applications open
Tell us what you are building, why now, and who is already backing you.
Applications take around 10 minutes. We review every submission and follow up within 5 working days. No pitch decks required upfront.
We review all applications. Applying does not guarantee listing.