Fintech Software Development Company in London, built to ship.

Money is not a float and a balance is not a column

Amounts are integers in minor units, and a balance is derived from an append-only ledger rather than stored and updated. Mutating a balance directly is the bug that produces money from nowhere under concurrency, and it is very hard to find afterwards because the audit trail is the thing you skipped.

Reconciliation is a daily product feature

Your ledger and the processor's settlement file will disagree, and the disagreement is normal: timing, fees, reversals, currency rounding. What matters is that a person can see the difference each morning and resolve it, which means reconciliation is a screen someone uses, not a script nobody runs.

Idempotency at every money-moving boundary

Networks retry. Users double-tap. Without an idempotency key on the payment intent, one intent becomes two charges, and the customer finds out before you do. Every write that moves value needs a key and a stored result for that key.

KYC and AML shape the data model, not just the signup flow

Verification state, document expiry, sanctions screening outcome and the reason for a decision all have to be modelled and retained, because a regulator will ask why a specific customer was approved in a specific month.

Working overlap

3.5 hours a day

Five and a half hours behind Surat in winter, four and a half in summer. The overlap is our afternoon and their morning, roughly 14:00 to 17:30 IST. That is enough for a daily call and not enough for continuous pairing, so the working agreement has to be written down rather than assumed.

The law that applies

the UK GDPR and the Data Protection Act 2018

The UK holds an EU adequacy decision, so EU-to-UK transfer is straightforward, but transfers onward to India need their own basis. In practice that means standard contractual clauses and a transfer risk assessment, and it is far cheaper to put those in place at contract signature than at go-live.

How buying works here

London buyers ask for references before they ask for a proposal, and financial services buyers will run a supplier assurance process that is longer than the build. Fintech and regulated work carry that overhead by default.

Procurement

Expect a security questionnaire, proof of insurance, and possibly a penetration test report. Budget the calendar for it.

Payments

Open Banking is further along here than almost anywhere, so account-to-account payment initiation is a realistic option rather than a novelty, and Faster Payments settles in seconds. Bacs Direct Debit still carries most recurring billing and its three-day cycle has to be modelled in the subscription state machine.