# Fintech App Development | KYC + Ledger + BaaS Integration | Alher Tech > Fintech apps that pass auditors: double-entry ledger, KYC/AML flows, idempotent payments, BaaS integration with Solaris/Treezor/Modulr. Spain & EU. - Canonical page: https://alhertech.com/en/solutions/fintech-app-development/ - Site: Alher Tech (custom software, AI agents and SEO engineering, https://alhertech.com/) - Contact: https://alhertech.com/en/contact/ --- Fintech apps where every cent is traceable, every flow is idempotent and auditors stop calling, built on a double-entry ledger you actually own. ## What Fintech App Delivers - **A Double-Entry Ledger as the Single Source of Truth**: Fintech is the category where shortcuts go to die. A naive payment record gets you to the first 100 users; the first regulator inspection or the first refund chargeback exposes everything that was hand-waved. We design for the audit on day one (double-entry ledger as source of truth, idempotency keys on every state-changing call, immutable event log), even when the MVP is small. - **KYC/AML Flows Designed for Real Conversion**: Onfido / Veriff / Sumsub integration with progressive disclosure: we don't ask for everything upfront, only what the user's risk tier requires. Drop-off down 30-50% versus generic providers. - **BaaS Integration That Survives Provider Changes**: A clean adapter layer above Solaris, Treezor, Modulr, Mangopay or Stripe Treasury so your business logic never depends on a single provider. Switching is a 6-week sprint, not a rewrite. - **Idempotent, Replayable Payments**: Every state-changing call has an idempotency key. Network retries, BaaS outages and duplicate webhooks cannot create double charges or double credits, properties verified by integration tests. - **Regulatory Reporting Already Wired**: SEPA INST, PSD2 SCA flows, Modelo 720/721 (Spain) for residency, transaction reporting for the Banco de España or local regulators. Built once, updated as regulation evolves. - **Fraud + Risk That Learns From Your Data**: Rules engine plus optional ML scoring on velocity, device, geography. Reviewable rules in Git, monitored false-positive rates, manual review queue with full context for the analyst. ## How We Build Your Fintech App - **Regulatory & License Discovery**: We map what your product actually does to the right regulatory framing (agent of an EMI, payment institution, money-remittance) so the build never collides with the compliance reality. - **Ledger Design**: Account chart, transaction types, fee accounting, FX handling. The ledger schema is the single most important decision; we get it right before writing UI. - **BaaS + KYC Integration**: Adapter layer with the chosen provider, full webhook coverage, retry/idempotency tested via simulated outages, KYC vendor with progressive UX. - **Money-Movement MVP**: One core flow live (top-up, transfer, card spend) with full audit and reconciliation. Closed beta with internal employees moving real cents. - **Pen-Test + Pre-Audit**: External penetration test, OWASP ASVS coverage, and a friendly pre-audit before the regulator meets us. We close findings before launch. - **Public Launch + Watchful Eye**: We sit with your team during the first month: fraud patterns and partner-outage modes only show up at real volume. ## High-performance stack used by global leaders React/Next.js/Angular on the frontend and Java 21 + Spring Boot + PostgreSQL 14 on the backend: the same stack that BBVA, ING, and Netflix use for their security and performance. ## Fintech App: FAQ ### Do we need a banking license to launch? Most fintech MVPs ship under a BaaS partner's license as their agent. Getting your own EMI or PSP license takes 12-24 months and €500K-€2M, usually not the right first step. We help you decide the path with regulatory counsel. ### How much does it cost? A focused fintech MVP (one core flow, KYC, single BaaS provider) is €120,000-€220,000. Multi-flow neobank-style apps with cards, FX and lending reach €350,000-€800,000+. ### How long to launch? 12-20 weeks to first audited transaction with one core flow. Full neobank-style products in 8-14 months. ### Which BaaS partners have you integrated? Solaris, Treezor, Modulr, Mangopay, Stripe Treasury and a couple of regional providers in Spain and LATAM. Our adapter layer means switching is contained, not catastrophic. ### How do you handle PSD2 SCA? Two-factor on every authentication and high-value transaction with biometric + device-bound key. We follow the EBA RTS and re-validate with each major version. ### Can it handle FX and multi-currency? Yes. Wise, Currencycloud or BaaS-native FX, with the ledger keeping each currency in its own accounts and FX rate snapshots stored per transaction for audit. ### What about cards? Virtual and physical cards via your BaaS partner or directly with Marqeta. Card issuance, controls (per-merchant blocks, daily limits, freeze/unfreeze) and 3DS, all in our toolkit. ### Do you work with clients globally? Yes. We work fully remote with clients across Spain, Europe, the US and LATAM. Time zones, video calls and live demos at every milestone.