An in-house bank-account service on the bank's API

The problem

A group of two legal entities runs all its settlements through a Belarusian bank. The bank's mobile apps disappeared from the App Store and Google Play: you can no longer install them on a new phone, nor update them. The bank offers a web version instead, one that installs on a phone like an app. It works — but it is universal, built «for everyone at once». And since account work was moving into the browser anyway, a fair question came up: why not build our own interface — for our entities, our scenarios and our CRM? Especially since long-standing pains had piled up that someone else's portal will never solve: there is no single screen with the overall cash picture, and the bank keeps only one year of history.

Before

• The bank's apps vanished from the App Store and Google Play — they can't be installed on a new device or updated.
• The replacement is the bank's web version: it works, but it targets every client at once rather than this company's specific tasks.
• No overall picture. Two entities, two portals with separate logins. To answer the simple question «how much money do we have in total», you had to log into both and add it up in your head.
• Awkward on the go. A generic third-party interface isn't tuned for glancing at balances or signing an urgent payment from a phone in seconds.
• Transaction history lives at the bank for one year only — anything older is simply unavailable, even though questions about old payments come up regularly.
• Account movements never met the CRM: the counterparty at the bank and the company in the CRM lived in separate worlds, reconciled by hand.

What we did

• An in-house web service on top of the bank's official API — our own interface instead of a generic one: balances across all accounts of both entities on a single screen, movements with filters and search.
• It installs on a phone too. Since the bank's replacement is a web version on the home screen, we built ours the same way: responsive layout, install-as-an-app. Except it opens straight on the screen you need — every account of both companies in a couple of seconds, no switching between portals.
• A permanent transaction archive. Every operation is stored on our side forever — the bank serves one year, while the in-house archive grows without limits. Plus a daily end-of-day snapshot of balances to see the dynamics.
• Payment orders: creation, templates and signing. Signing happens on the bank's own page — the SMS code is entered at the bank, not in our service, so the standard security perimeter isn't weakened. A batch of documents can be signed with a single code.
• Access for colleagues with different rights, plus an action log: who did what to which payment and when.
• Every movement is automatically mirrored into a Bitrix24 list and linked to the CRM company by tax ID — finance and the client base finally meet in one place.

Results

• Both legal entities in one interface, regardless of whether the bank's applications work today.
• The answer to «how much money do we have» is one screen instead of two portals and mental arithmetic. From a phone, in seconds.
• The entire available year of transaction history for both entities was pulled in at launch — from there the archive grows forever and history no longer disappears.
• Balances and movements are pulled from the bank automatically; an end-of-day snapshot is recorded for every account — you see the trend, not just «right now».
• Account movements are visible right in the CRM and tied to the counterparty's company card — no more manual matching of bank and clients.
• The payment flow works from our own interface: signing of live payment orders has been proven in production and documents reach the bank.