How Decisis answers a research question.
This page is the durable description of what the system does, how it fails safely, and what authority is in the corpus across income tax, transfer tax, and cross-border tax research — equal use cases for the CPAs, tax attorneys, estate planners, and wealth planners who rely on it. It is the page that does not exist at competitive AI tools. Its presence is the point.
Source acquisition
Title 26, Treasury Regulations, IRB-published guidance, written determinations, court opinions, state codes, treaties, and uniform acts — pulled from the official authoritative sources and refreshed continuously. No third-party rewrites, no aggregators that drift, no summaries treated as law.
Structured sources
Tax law is hierarchical. Sources are preserved with their full citation context so every retrieved passage is independently cite-able. The structure of the authority — its place in the section, its parent, its effective period — is a first-class field, not text to be re-parsed at query time.
Hybrid retrieval
Each question is rewritten into a structured plan — jurisdiction, document type, time horizon, scenario — and multiple retrieval paths run in parallel. Results merge, get re-ranked against the question, and expand one hop through the citation graph before synthesis sees them.
Synthesis with citation enforcement
Synthesis is deterministic. No substantive claim ships without a pinpoint cite drawn from the sources block; the sources block is the only authority; conflicts are surfaced explicitly; non-precedential authority is flagged; statute, regulation, ruling, and case are distinguished.
Post-synthesis verification
Every inline citation is verified to resolve to a real authority in the corpus. Any unresolved citation triggers regeneration. This catches anything that slips through prompt enforcement.
Refusal layers
Two refusal layers. If the retrieved authority does not clear a relevance floor, synthesis is skipped and the practitioner sees suggested next-step references instead. The synthesis layer also refuses when the source set is insufficient. Refusal rate on the out-of-corpus eval set: 96.8%.
Currency tracking
Every authority carries an effective date and supersession status. Historical authority is flagged as historical; current law wins. Major statutory shifts propagate automatically — pre-2026 TCJA sunset planning, for example, is treated as historical context after OBBBA.
Audit and reproducibility
Every output ships with a versioned trail of the sources and operations that produced it. A practitioner running the same question against the same corpus gets the same answer. The firm's audit retention follows state-bar policy.
Evaluation
Continuous eval against 200+ hand-curated estate/tax research questions with attorney-verified ideal citations, plus dedicated sets for out-of-corpus refusal, conflict surfacing, and currency accuracy. Every change is gated on the eval. Regressions block merge.
Last reviewed by Director of Legal Content · 2026-05-10