Merchant onboarding for SME payments. Pre-seed. Forty merchants onboarded in the first quarter, all by hand because the KYC checks felt risky to automate. Three engineers and a regulatory advisor. Then the FCA registration came through, and volume ramped.
Industry Fintech development · FCA-aware · PCI-aware · PSD3-aware · UK
Fintech development, built to the regulator’s. question, not the demo’s.
Fintech development for UK founders, banks, and B2B payments teams. Payments, wallets, lending, and settlement built with FCA-aware design, PCI-DSS scope awareness, PSD3 readiness, Open Banking AISP / PISP, KYC + AML triage, and idempotent money flows — on MERN + Python + AWS.
24hreply, from a senior
200+projects shipped since 2019
Senioronly, on the spine
(Why UK fintech founders sign)
Your regulator and your acquirer ask the same questions. We build to the answers.
FCA-compliant fintech development isn’t a feature you bolt on at audit. It’s a set of decisions you make in week one, or pay nine months to retrofit. We make them in week one.
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The founder this page is for6-week KYC backlog · £180K missed · 4 hours
Henry founded a UK fintech. The product worked. The compliance didn’t scale.
Forty merchants a month became four hundred. The manual KYC backlog stretched to 6 weeks. A sanctions list update fired in March. One on-boarded merchant matched. By the time the team noticed, that merchant had moved £180,000 through the platform. Henry filed the SAR himself. The board call was not pleasant.
We built the compliance agent over fourteen weeks. KYC + AML triage on document ingest. Sanctions screening against UK + EU + OFAC lists, refreshed daily. Audit log on every decision. 82% of merchants auto-approved. This page is for the fintech founder who’d rather build to the regulator’s question on day one.
HIRE FINTECH DEVELOPERS LONDON · SENIOR-ONLY STUDIO
Four things a generic SaaS shop can’t hand you
This is what nine UK fintech builds have hammered into the studio. Not a brochure. The reasons founders, banks, and B2B payments teams trust us with real money flows.
FCA-aware from day one
Your model is mapped against the FCA permissions you’ll need in week one. The architecture documents the permissions boundary, so your compliance lead reads it and signs, not retrofits it nine months later.
Double-charges, architecturally impossible
Every payment write is idempotency-keyed. The reconciler verifies PSP events against your DB nightly. Zero double-charges, zero sanctions breaches across nine fintech platforms in production.
An audit log your regulator reads cold
Every customer decision logs actor, decision, reasoning, policy clause, and timestamp. Exportable per customer, per date range. The supervisory response writes itself. Three FCA-style reviews passed first time in 2025.
A real reply in 24 hours
Mohit reads every brief personally. A real reply, not a calendar link, inside one working day. London time.
The fintech pain. The architectural answer.
Every fintech founder who emails us is fighting one of these eight things. Each one is brutal to fix once money is flowing. Each one is a single architectural decision made on day one of our build.
- 01
“A sanctions list update fired. We didn’t catch it for three weeks. The SAR was awkward.”
Daily-refreshed sanctions screening + audit log. OFSI + EU + OFAC + UN lists refreshed daily. Every customer rescreened nightly. Anomalies escalate inside the hour. The audit log shows when each customer was screened against each list.
- 02
“Our Stripe webhook double-fired during a retry storm. Customers charged twice. Refunds manual.”
Idempotency keys + nightly reconciler. Every payment write is idempotency-keyed. The reconciler verifies Stripe events against our DB nightly. Refunds reissue invoices automatically. Double-charges become architecturally impossible.
- 03
“Our auditor said we’re in SAQ-D scope. The audit will take six months and cost £80K.”
Tokenisation moves you to SAQ-A or SAQ-A-EP. Card data never touches your servers. Stripe / Adyen / Worldpay Elements on the front end. Your scope drops to SAQ-A or SAQ-A-EP. Audit goes from months to days.
- 04
“Manual KYC took 6 weeks at 400 customers a month. The pipeline backed up. Conversion dropped.”
Compliance agent with 82% auto-approval. Document review + policy rule engine. 82% auto-approval. 18% escalate to a human with reasoning attached. Median KYC time drops from 6 weeks to four hours.
- 05
“An FCA supervisory letter is coming. We have no audit log, no documented compliance flow.”
Append-only audit log + flow documentation. Every customer decision logs actor, decision, reasoning, policy clause cited, timestamp. Exportable per customer, per date range. The supervisory response writes itself.
- 06
“SCA exemption changes are coming. We don’t know what falls under TRA, low-value, or trusted beneficiary.”
3DS2 with exemption routing + frictionless flow. 3DS2 wired with intelligent exemption routing. Low-value, TRA, trusted beneficiary all evaluated per transaction. Frictionless flow where allowed. Step-up auth where required.
- 07
“EMI rules require segregated safeguarding accounts. We have one bank account.”
Ledger-first design + tiered safeguarding. Double-entry accounting in the platform. Customer funds segregated in safeguarding accounts. Tier-1 (high-quality liquid assets) and Tier-2 (insured deposit). FCA EMI rules built into the data model.
- 08
“Series A diligence asks about technical risk. We have no architecture brief.”
FCA-aware architecture brief + ADRs. A 30-page brief written to the regulator’s question. Six ADRs minimum. Threat model. Sanctions process. Reconciliation flow. Your acquirer’s CTO reads it once and stops asking.
FINTECH SURFACES WE’VE SHIPPED
Eight fintech surfaces, live in production
What lives on the money spine. Each one wired idempotent, audit-logged, and built so your reconciler agrees with your bank statement.
Card + ACH payments
Stripe / Adyen / Worldpay tokenised. 3DS2. SCA-compliant checkout. Idempotent webhook handlers + nightly reconciler. GBP, USD, EUR.
UK Direct Debit (Bacs)
GoCardless for one-off + recurring DD. Bacs lifecycle handled. Failure recovery, retries, customer comms via Resend / Postmark.
Open Banking (AISP + PISP)
TrueLayer / Plaid / Tink. Account information, transaction history, payment initiation. Strong Customer Authentication baked in.
KYC + AML + sanctions
Onfido / Veriff / Sumsub for identity. PEP + OFSI + EU + OFAC screening, daily-refreshed. Decisions with reasoning, audit-logged.
Lending + credit decisioning
Score models in Python. Credit bureau integrations (Experian, Equifax, ClearScore). Affordability flows. Open Banking cashflow analysis.
Wallets + stored value
Ledger-first accounting. Double-entry by default. Tier-1 + Tier-2 wallet design for FCA EMI safeguarding rules.
Settlement + reconciliation
Multi-leg settlement workflows. Counterparty net-off. Nightly reconciliation against bank + PSP statements. CSV export for finance.
Risk + fraud monitoring
Velocity rules. Device fingerprinting. Stripe Radar where applicable. Custom rules engine for product-specific signals.
Three tiers, one ledger that survives the audit.
Nine UK fintech platforms have stress-tested these picks. Tier 1 runs every build. Tier 2 is what we reach for when the brief needs it. Tier 3 scales it to bank-grade volume.
T1
What every fintech build runs on
MERN + PythonMongoDBPostgreSQL (ledger)Node.js + ExpressReact + Next.jsTypeScriptPython (FastAPI)Stripe + AdyenGoCardlessTrueLayer / PlaidOnfido / VeriffComplyAdvantageMixpanel
T2
When your fintech brief calls for it
reach when neededWorldpayModulr / BottomlineExperian / EquifaxSumsubCurrencycloudJava + Spring
T3
The infrastructure that scales it
AWS + cloud-nativeAWSRDS / AuroraAWS KMSSecrets ManagerKubernetes (EKS)Apache KafkaSQS + EventBridgeRedisTerraformDatadog + SentryVanta / DrataMicroservices
Recent client · UK fintech · 2024
6-week KYC backlog to
6-week KYC backlog to
four-hour decisions, FCA audit passed first time
Henry’s merchant onboarding compliance agent, in real numbers. We rebuilt the manual KYC backlog as a state machine that reads documents, runs against policy + Companies House + UK + EU + OFAC sanctions lists, drafts a recommendation, and escalates only the unclear cases. Fourteen-week sprint, behind a feature flag.
The sprint
14wk
Compliance agent shipped
82%
Merchants auto-approved
The outcome
0
Sanctions breaches
68%
Senior compliance time cut
Track record
9
Fintech platforms since 2019
100%
FCA-style audits passed
Three ways to start. Pricing in the email back.
We don’t publish prices on a page. Every fintech scope carries different regulatory weight. Pick the shape that fits and Mohit will send your real number inside 24 hours.
Fintech audit week
One week, fixed cost. A 30-page brief mapping your build against FCA permissions, PCI scope, PSD3 readiness, and AML obligations.
- 5-day senior audit
- Regulatory mapping
- Architecture brief + ADRs
- No commitment to build
Fintech build sprint
8 to 14 weeks. Full fintech surface end-to-end. Payments, KYC, AML, audit log, reconciler. FCA-aware from day one.
- MERN + Python + AWS
- FCA + PCI + PSD3 designed in
- 30-day walk-away both ways
- IP assigns on every commit
Compliance rebuild
7 to 12 weeks. Your existing fintech with the FCA letter or supervisory request. We rebuild the gaps and ship the audit log.
- Gap audit + remediation
- Audit log retrofit
- Sanctions process rebuild
- FCA-style brief shipped
“The audit log was the document that closed our supervisory file. They read it once and stopped asking.”
— Henry, founder, UK payments fintechWhat fintech founders actually ask before signing
Pain-first, soft-second. The questions every founder asks before they trust an engineering studio with real money flows.
No, and we don’t need to be. We build the platform. Your FCA permissions sit with your firm. Our job is FCA-compliant fintech development: ensuring the architecture and operational flows give you a clean audit trail when your supervisory contact at the FCA opens the file. We’ve shipped nine UK fintech platforms since 2019. Three passed FCA-style review in 2025.
Not directly. That’s regulatory consultancy work, and we’re engineers. We do work alongside three UK FCA consultancies regularly (introductions available) and produce the technical evidence pack they need for your application. Most of our fintech clients arrive having already started or completed FCA registration.
Tokenisation. Card data never touches your servers. Stripe Elements, Adyen Components, or Worldpay Hosted Fields capture the card on the client and exchange it for a token. Your servers handle the token, not the PAN. Your PCI scope drops from SAQ-D (months of audit) to SAQ-A or SAQ-A-EP (days). It’s designed in at week one of the build.
Yes, with the compliance agent we ship. Median 82% auto-approval across our fintech clients. 18% escalate to a human with reasoning and policy clause cited. KYC time drops from weeks to hours. Henry’s case study above ships 4,000 merchants a month on this exact shape. Custom fintech software development at this volume is what we do.
ComplyAdvantage or Sumsub by default. UK OFSI + EU + OFAC + UN lists refreshed daily. Every customer rescreened nightly. A hit triggers an immediate freeze on outbound payments, an audit log entry, and an alert to your compliance lead. SAR exports built into the dashboard. Zero sanctions breaches across nine fintech platforms in production.
Three things make this hard to fake. The 30-day walk-away clause goes both ways and refunds the unused portion. Payments are milestoned 25/25/25/25, so you never pay more than 25% ahead of working software. And we’ve been shipping since 2019, UK VAT registered, listed on Companies House. You can check us before you sign.
Yes, with 14 days’ notice. Engineers move to other projects, your repo stays where it is, your spend pauses. Resume with 14 days’ notice and we pick up at the same sprint board, same engineers. No cancellation fee, no restart fee. We’ve done this six times in 2025.
That’s the whole point of fintech development done our way. You get a 30-page FCA-aware architecture brief, six ADRs minimum, a threat model, the documented sanctions process, and the reconciliation flow. Three 2025 clients passed acquirer or regulator reviews on first walkthrough. The brief is written to the question your acquirer’s CTO will ask, so they read it once and stop asking.
In context
The surface you hand over.
fintech development, in context — the dashboards, flows and components your team actually ships, reviews and maintains.
One paragraph. That’s it.
Tell us the FCA permissions in play, the payment surface you’re building, and the volume target you’re holding to. Mohit reads every first email and replies inside 24 hours: a clear yes, a clear no, or the one question that decides it.
What happens after the email lands
- < 24h
A personal reply.
Yes, no, or the deciding question. Straight to your inbox, not a team thread.
- Week 1
Audit week begins.
We map your build against FCA permissions, write the trade-offs, hand you a signed scope.
- Week 14
Audit-ready fintech.
Payments, KYC, AML, reconciler, and the brief your regulator and acquirer both read cold.