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Built inside a tax practice

Tax preparation.
From the source.

End to end. Preparer led.

From source documents to a finished return package. Built for the way tax professionals actually work.

Explore the S-Corp Engine

S corporations first. Form 1040 comes next.

  1. Source documentsEvidence comes first
  2. Reviewed factsPreparers establish authority
  3. Deterministic tax logicRepeatable calculations
  4. Forms & workpapersA return you can explain
A clear path to the returnS-Corp Engine · Alpha 14
S-Corp Engine / actual workspaceSynthetic example
PrepReturns Forms Mode showing the synthetic Juniper Form 1120-S and saved return package.
Actual IRS forms. The evidence, decisions, and calculations stay within reach.Synthetic example · Click to inspect
Built by Trio TaxProfessional judgment stays in controlActual forms. Visible calculations.

A tax firm first

Better tools start with the people using them.

Trio Tax

We didn’t start a software company and go looking for a tax problem. We run a tax firm. We built the software we wanted to use.

PrepReturns grew out of Trio Tax: client documents, books, payroll, basis, and all the awkward handoffs between them.

The story behind PrepReturns

Deliberately focused

The straightforward 90%.

Straightforward doesn’t mean small. Conventional businesses with real payroll, assets, owners, and tax decisions. Built around the patterns professionals see again and again.

Multiple ownersPayrollBasis & loansAssetsInventoryRentals

“90%” is our design ambition, not a measured coverage claim.

Explore the intended return universe

One philosophy. More possibilities.

S corporations first.
Individuals next.

Evidence, explicit unknowns, and professional review. Form 1040 will carry the same ideas into a domain built for households.

1120-SThe first PrepReturns engine
1040 ↗Coming next

The preparation path

End to end means
end to end.

Review the evidence. Make the tax decisions. Calculate, inspect, and produce the return.

01 / Start with what you have

The work begins with the sources.

Financial statements, prior returns, payroll, asset schedules, and shareholder support belong in one preparation path. Supported imports propose facts. The preparer establishes what can be used.

Follow the workflow
S-Corp Engine / actual workspaceSynthetic example
PrepReturns Start workspace with synthetic Juniper, Alder and Cedarline examples.
A working preparation system, developed through successive Alphas.Synthetic example · Click to inspect

02 / Review, don’t retype

The source stays in view.

A number on a return should have a history. Confirm what’s right, correct what isn’t, and preserve the original evidence.

Explore source provenance
S-Corp Engine / actual workspaceSynthetic example
Source review showing the synthetic Alder financial statement and proposed values.
Review proposed source values before they become preparation facts.Synthetic example · Click to inspect

03 / Make the professional decisions

Ask for what the evidence can’t answer.

Guided Preparation focuses attention on unresolved facts, elections, and treatment decisions. Direct forms, workpapers, and diagnostics remain accessible.

Explore Guided Preparation
S-Corp Engine / actual workspaceSynthetic example
Guided Preparation showing source-review tasks for the synthetic Alder case.
The workflow follows the return; the preparer retains control.Synthetic example · Click to inspect

AI-assisted development. Deterministic tax.

AI helped us build it.
It doesn’t get to improvise
your tax calculation.

Frontier models helped with research, implementation, testing, and fresh review. The calculation engine is explicit software: established facts go in, reproducible results come out.

Every Alpha brought new questions about sources, ownership, basis, saved history, and output. Each generation had to protect what came before.

Follow the development story

Built in Alphas

It took a lot of work
to make the work simpler.

Inside the development
  1. Alpha 01–03

    Prove the tax core

  2. Alpha 04–08

    Connect the sources

  3. Alpha 09–11

    Guide the preparer

  4. Alpha 12–13

    Produce the return

  5. Alpha 14

    Broaden the business scope

Alpha 14 — human testing and broader operating-business coverage. The next engine is Form 1040.

From the practice

More than a feature list.

From the journal

The open-source direction

Tax software you can actually change.

Read the essay

From the practice

A sales demo isn’t a test drive.

Read the essay

Inside the engine

Every number needs a story.

Read the essay

Professional software can be incredibly capable.
It can also be frustrating.

Constrained demos. Difficult technical support. Bugs and regression work. Expensive or incomplete APIs. Feature requests that disappear into a backlog. We wanted a different relationship with the tools we use.

Why another tax program?

The open-source direction

Built to be opened.

PrepReturns is private today and likely to become open source. The goal is software practitioners can inspect, modify, integrate, extend, and contribute to.

That future requires a published license and a contribution process. The direction is clear: professionals should be able to help shape their tools.

Why open source matters

The Trio ecosystem

Built from the practice outward.

01 / The practice

Trio Tax

The tax practice where the PrepReturns problem started.

Visit Trio Tax
02 / The books

Trio Ledger

A sibling ledger product for very small businesses and useful financial statements.

Visit Trio Ledger
03 / The return

PrepReturns

Professional tax preparation, beginning with S corporations.

Explore the project

Related projects with a shared practical origin. An implemented integration is not implied.

Help shape what comes next.

Tax professionals, engineers, researchers, and software companies: let’s compare notes.

Let’s collaborate

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