Finance & Tax
An open-source language for financial decision logic. Readable by auditors, bound to time, mathematically exact, and entirely under your control.
The problem
Tax codes and compliance mandates are encoded across mainframes, microservices, and vendor platforms. Proving how a calculation was reached requires reconstructing logic from application code.
Regulators require proof of how outcomes were reached. When logic is distributed across systems, producing that proof is an expensive reconstruction exercise.
Rules change annually but prior versions remain in force for open positions, audits, and retroactive adjustments. Standard architectures handle this with fragile date branching.
Financial rules operate in exact units. General-purpose languages default to floating-point, introducing rounding errors that surface during reconciliation.
Introducing Lemma
Lemma is a declarative language that separates decision logic from application infrastructure.
Every evaluation produces a step-by-step trace showing which rules applied, with what inputs, and in what order.
Maintain concurrent rule versions. The engine routes each evaluation to the correct version based on the effective date of the transaction.
Custom types with explicit units (EUR, USD), arithmetic without losing precision, even over time.
Publish a rule once in LemmaBase. All downstream applications query the same versioned, governed source.
Why LemmaBase
Open-source foundation. No vendor lock-in. Deterministic by design.
We work with institutions to separate decision logic from application code. Get in touch to learn more.