We Have Worked With
Modern Treasury development, done by payment engineers
Modern Treasury gives you one API for moving money — ACH, wires, RTP, FedNow, and more — across 30+ direct bank integrations, with ledgers, virtual accounts, and reconciliation built in. But the API being clean doesn't make payment operations simple. Double-entry ledger design that has to be right before the first transaction posts. ACH returns and reversals arriving days after you thought money moved. Webhook handling where a missed event means a wrong balance. Reconciliation rules that work in the sandbox and break on real bank statements. This is where payment projects quietly go sideways.
FintegrationFS is a fintech engineering studio, not a staffing marketplace. Our engineers have spent 12+ years building money movement, ledger, and reconciliation systems for fintechs and platforms — and we're official technology partners of payment infrastructure providers including Plaid and Straddle. US office, senior engineering team, and a fixed-scope model so you know cost and timeline before we start.
Which Modern Treasury products does your build need?
Modern Treasury is modular, and scoping the right combination up front is the difference between a six-week build and a six-month one:
Payments — payment initiation and tracking over ACH, wires, RTP, FedNow, and checks through your bank relationships (or Modern Treasury's integrated PSP to start faster).
Ledgers — an immutable, double-entry ledger API for tracking user balances and money movement at scale. Powerful, but only as good as your ledger model.
Virtual Accounts — programmatic sub-accounts that automatically attribute incoming payments to the right customer. Essential for platforms collecting on behalf of many users.
Reconciliation — rules that match expected payments to bank transactions as they post, including returns and reversals matched back to the original payment.
Counterparties and compliance — onboarding, verification, approval workflows, and audit trails around every payment.
Not sure whether you need Ledgers, Virtual Accounts, or both? That's the first thing we resolve in a free scoping call.
What our Modern Treasury developers build
Payout and collection automation. High-volume disbursements and pull payments with approval rules, batching around bank cutoffs, retry logic, and real-time status tracking through webhooks.
Ledger architecture and implementation. Designing your double-entry ledger model — accounts, categories, and transaction flows — before writing code, so balances stay correct through refunds, reversals, and edge cases, not just the happy path.
Virtual account platforms. Programmatic account creation and automated attribution of incoming funds for marketplaces, PropTech, lending, and B2B platforms collecting for many customers at once.
Reconciliation and close automation. Expected-payment workflows and reconciliation rules that match bank activity automatically — including ACH returns, NOCs, and reversals — so your finance team stops closing the month in spreadsheets.
Webhook and event infrastructure. Idempotent event processing, ordered handling, replay protection, and alerting — because in payments, a dropped webhook isn't a bug, it's a balance discrepancy.
Integration rescue and audits. Inherited a Modern Treasury integration with drifting balances, unmatched transactions, or webhook handlers nobody trusts? We audit the ledger model, event handling, and reconciliation rules — then stabilize and document.
How we work — fixed scope, no surprises
Free scoping call (30 minutes). We map your money movement flows to the right Modern Treasury products and your bank setup.
Architecture and a fixed quote. Ledger model, payment flows, and event handling designed up front — with a fixed price and fixed timeline.
Build in weekly sprints. Everything validated in Modern Treasury's sandbox first, including simulated returns and failure cases — not just successful payments.
Go-live and support. Staged rollout with reconciliation monitoring, alerting, and documentation your team actually owns.
What a Modern Treasury engagement looks like
Marketplace payouts at scale. Automating seller disbursements: counterparty onboarding, batched ACH and RTP payouts with approval controls, webhook-driven status updates back into the product, and returns handled without manual intervention.
A wallet or stored-balance product. Designing the double-entry ledger for user balances, wiring deposits and withdrawals through Payments, and keeping the ledger provably in sync with bank reality through continuous reconciliation.
B2B collections with virtual accounts. Issuing a virtual account per customer so incoming wires and ACH credits attribute automatically — eliminating the "who paid us?" spreadsheet and cutting days off cash application.
Who hires our Modern Treasury developers
Fintech startups — wallets, lending, and payment products on solid ledger foundations
Marketplaces and platforms — payouts, collections, and balance tracking for many parties
B2B software companies — embedding money movement into existing products
Finance and treasury teams — automating payment operations and month-end close
PropTech, InsurTech and healthcare platforms — high-volume, compliance-sensitive money movement
Tech stack: Node.js · Python · Ruby · Java · REST APIs and webhooks · PostgreSQL · Kafka · Redis · Docker and Kubernetes · AWS, GCP and Azure
Modern Treasury development FAQs
Why use Modern Treasury instead of integrating directly with our bank?Direct bank integrations mean file formats, SFTP, per-bank quirks, and months of work per bank — then you still have to build ledgering and reconciliation yourself. Modern Treasury abstracts that behind one API. Our job is the layer above: your ledger model, payment flows, and event handling, done right.
Do we need our own bank relationship to use Modern Treasury?Not necessarily to start. Modern Treasury offers an integrated PSP route to begin moving money quickly, and you can add direct bank relationships as volume grows — within the same integration. We help you scope which path fits your stage and volumes.
Can you design our ledger model, not just implement it?Yes — and you should insist on this. Most ledger problems are modeling problems: which accounts exist, what a transaction touches, how refunds and reversals post. We design the double-entry model with you before writing code, because migrating a wrong ledger model in production is painful.
How do you handle ACH returns and reversals?As first-class flows, not edge cases. Returns can arrive days after settlement, so we build expected-payment matching, automated return handling with ledger corrections, and alerting for anything that needs a human — before go-live, not after the first R01.
Can you migrate our existing payments or ledger stack into Modern Treasury?Yes. We run migrations as parallel systems: historical balances reconciled into the new ledger, both systems compared until they agree, then a staged cutover with a rollback plan. No big-bang switches with customer money.
How long does a Modern Treasury integration take?A focused payout automation: 2–4 weeks. A ledger-backed wallet or virtual account platform: 4–8 weeks. Complex migrations or multi-product builds: 8–12+ weeks. You get a fixed timeline in the quote, not an estimate that drifts.
How much does it cost to hire a Modern Treasury developer?We quote fixed-scope projects after a free scoping call, so you know the full cost before we start. With money movement, fixed scope also means fixed accountability — you're not paying hourly for someone to learn reconciliation on your ledger.
Do you sign NDAs? Who owns the code?NDAs are standard before any technical discussion. You own 100% of the code and IP — delivered in your repositories and documented for your team.
Book a free Modern Treasury consultation
Tell us how money needs to move through your product — and a senior engineer, not a salesperson, will come back within one business day with an honest read on scope, ledger design, and timeline.
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