INSIDE THE SYSTEM
The architecture follows the professional work: preserve the evidence, establish the facts, calculate deterministically, explain the result and produce the return.
THE CONCEPTUAL ARCHITECTURE
A source parser, a tax rule and a PDF renderer each have a job. Separating those jobs makes it possible to challenge a result without treating the entire system as a black box.
See the practitioner’s viewEvidence
Original bytes and identity are retained. Supported source formats have explicit extraction contracts.
Interpretation
Bounded deterministic extraction yields reviewable readings, with source locations and periods.
Authority
Accept, correct, exclude or establish facts. Tax treatment and elections remain explicit.
Calculation
One normalized preparation model feeds ordered rules, explicit money handling and cross-checks.
Explanation
Supporting calculations explain results. Optional diagnostics inspect the saved preparation.
Output
Applicable forms, owner deliverables and internal workpapers share saved output and a manifest.
THE DETERMINISTIC CORE
The tax engine uses explicit money handling, calculation order and rounding. It does not ask a model to improvise a deduction. Results can be reproduced, compared against independently derived expectations and traced through workpapers.
The boundaries between calculations matter as much as the arithmetic. Corporate allocations remain full even if one owner lacks basis. Book equity is not tax basis. A loan’s principal is not necessarily its tax basis. Those concepts have distinct records and rules.
A missing fact withholds a dependent conclusion. It need not erase unrelated valid information: unknown shareholder basis does not make known corporate interest income disappear.
Why determinism mattersFACT AUTHORITY
A source reading and a preparer decision carry different authority. Accepted source facts, manual entries, corrections and unresolved conflicts must remain distinguishable. A newer file is not automatically a better answer.
The retained source supports future review. Correction history records what changed without altering what the original document reported.
Explore the evidence modelEXPLICIT STATE
Unknown, known zero, not applicable and unsupported cannot safely collapse into one empty field. Applicability depends on established facts; a form is not omitted merely because the engine has no value for it.
Those distinctions also inform the preparer’s next action. A missing fact calls for evidence. An unsupported structure calls for a different preparation path.
A SAVED PREPARATION
A prepared package binds the calculation, explanations and output to a particular saved state. Its manifest identifies the documents and their corporate, shareholder or internal-workpaper roles.
Printing selects saved output. It does not run another tax engine. Owner-scoped selection checks that private shareholder documents belong to the selected owner.
After an input changes, old output remains historical. A new preparation establishes the current package. That is a product behavior with engineering consequences: dependencies, integrity checks, stale-state handling and visible labels all have to work together.
The difficult engineering behind itACTUAL FORMS
Official-form output uses pinned IRS templates and versioned mappings. The preparation determines applicability and instances; the renderer places the saved values on the relevant forms and supporting pages.
Correct field mappings alone are insufficient. Text can exist in a mapping ledger and still fail to appear on the visible page. The development process therefore inspects downloaded PDF content and rendered appearance, as well as the underlying calculation.
That also explains why a template inventory is not a capability list. A supported form needs the right inputs, calculations, selection rules, explanatory information and tests.
THE AI BOUNDARY
Frontier models support research, implementation, test creation, fresh review and iteration under human direction.
The current runtime source parsers are deterministic. They process supported structured exports and bounded text-PDF layouts. The retained implementation evidence does not establish LLM extraction, OCR or universal document understanding.
Broader ingestion can develop without changing the authority model: a proposed fact still needs review, and an AI-assisted document workflow would not become the tax calculator.
Independent model review adds a useful challenge to the work. It is not independent professional certification. Tax-professional judgment remains the final authority.
See the development processLOCAL-FIRST HERITAGE
The engine began as a local workspace with a browser interface and local case storage, rather than a consumer cloud service. Source preservation, recoverability and professional control shaped its architecture from that starting point.
This public website is a separate static showcase. It does not run the tax engine or accept taxpayer uploads. A future hosted environment would require its own data-handling and security design.
Form 1040 will carry forward the evidence and review principles with a separate household domain. The goal is shared contracts at useful boundaries, not one giant universal tax object.
The next domain: individual returnsWe welcome conversations about preparation models, professional workflow, integrations and the open-source direction.
