Now onboarding founding merchants
1.8% flat card processing for UK SaaS and digital product businesses that tracks every payment through seven explicit states so you always know exactly where your money is.
Visa, Mastercard, Apple Pay and Google Pay, with a full audit trail on every transaction.
A clean checkout with card details, Apple Pay and Google Pay all in one place. Fully hosted, so there's zero PCI scope on your end. One API call to create a session and your customer sees your brand name and a payment form on any device.
Your server creates a checkout session, you redirect the customer to the URL we return and they pay. Fluxa handles the card form, security and state tracking. No frontend SDK, no PCI scope and no webhook maze.
// Create a checkout session curl https://api.fluxapay.co.uk/v1/checkout \ -H "Authorization: Bearer sk_live_..." \ -d amount=4999 \ -d currency=gbp \ -d description="Monthly subscription"
{
"id": "cs_8f2a...",
"url": "https://pay.fluxapay.co.uk/cs_8f2a...",
"state": "PAYMENT_RECEIVED",
"amount": 4999,
"fee": 90
}
The fee is in the response. You know what you're paying before the customer even enters their card.
Revenue, payouts and every transaction with its full timeline. You see the exact fee on every payment, the feed updates in real time and you get flagged when anything looks off.
Seven explicit states with only one valid action at a time, you can't skip steps and every transition is enforced, logged and permanent.
Most payment systems treat money as either "in" or "out," and that's where the mistakes hide. Fluxa forces every stage to be acknowledged, so reconciliation is simple and disputes are easy to resolve.
1,325 automated tests across 16 test suites verify every state transition, every guard, every edge case and every concurrent race condition. The state machine is proven in code, not promised in a pitch deck.
A flat percentage and nothing else, no per-transaction fixed fee, no cross-border uplift, no monthly minimum and no surprise add-ons. The number on the tin is the number you pay.
Invite-only and locked for 12 months from the day you go live, with just ten spots available.
Standard rate after your founding year ends, with the same flat structure, same transparency and same terms. No lock-in and you can cancel any time.
Put your numbers in and see the gap between Stripe's headline rate and what you're actually paying them each month.
Based on Stripe UK published rates (1.5% + 20p domestic, +1.5% cross-border, +0.8% corporate card uplift, 2p Radar fee per transaction). Actual rates may vary. Want the exact number? Send your Stripe fees page to us.
For companies that can't afford unreliable payments.
Seven money states, each enforced and logged as they happen, you can't skip steps, you can't move backwards and the state machine is the single source of truth for every payment.
Every financial movement is recorded as a double-entry posting, running independently of the state machine so you've got a second check on everything.
Token-based auth with role-based access, so every action is tied to a specific operator identity and shows up in the audit trail.
Spots failure spikes, volume drops, stuck checkouts and other patterns that look wrong, with 223 tests behind it.
If two operators try to approve the same payout at once, only one of them can actually send it. Row-level locking in Postgres makes sure of that.
If an external service fails, Fluxa stops retrying and fails safely instead of cascading the problem. You can also preview any dangerous action before you commit.
I built Fluxa because I got tired of payment systems acting like money is either in or out, when the bit in the middle is where the problems usually are. Every line of code in this system is mine, from the state machine and the double-entry ledger through to the checkout, the dashboard and the 1,325 tests that verify it all works.
My partner runs compliance and reconciliation, so when you email support@fluxapay.co.uk you're talking to the people who built it, and that's not going to change.
LinkedIn1.8% flat, locked for 12 months, with the people who built the system answering your emails. Drop your address below and we'll talk properly.
Bootstrapped, no investors and answering every email ourselves.