Money software that is correct by design.

1/4A customer pays

2/4Authorized in milliseconds

3/4Recorded twice, balanced always

4/4Settled and reconciled

Follow one card payment through the system.

Payments, card programs, ledgers, and reconciliation, built so every cent is accounted for.

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What we build

  • Card programs

    Virtual and physical cards with an issuing partner: onboarding, spend controls, authorizations, and disputes.

    card.authorization.approved

  • Payments and wallets

    Deposits, withdrawals, and transfers across cards, bank rails, and crypto networks.

    Crypto rails are built with our On-chain systems practice.

    transfer.settled

  • Ledgers

    Double-entry ledgers with a full audit trail, so every balance can be explained.

    journal_entry.posted

  • Reconciliation

    Automated matching against provider and bank reports, with exceptions flagged before they become losses.

    recon.exception.opened

  • Compliance-ready flows

    Identity verification, transaction limits, and the records auditors ask for.

    kyc.verified

How we build money software

Idempotent by default

A retried request never charges twice.

Every balance has a history

Balances come from ledger entries, never edited in place.

Reconcile every day

Our numbers are checked against the provider's numbers, automatically.

Failure is part of the design

Timeouts, out-of-order webhooks, and provider outages are planned for, not discovered.

Case study

A crypto-funded card program

We built the platform behind a card program that lets customers fund their cards with crypto and spend anywhere cards are accepted.

What we built

  • Card issuing integration with a regulated partner
  • Crypto deposits across multiple blockchains
  • Customer onboarding with identity verification
  • Double-entry ledger with daily reconciliation
  • Admin and support tools for the operations team

Contact

Building something that moves money?

Tell us about it. We will tell you what we would build first.

Email
gustavo@tavin.dev
Include
What it should do, who uses it, and any deadline.
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