Marble

Ask Marble a tax question and it returns a written answer with inline citations, and the citations open. That last part is the whole test for this generation of tools, and Marble answers it by shipping the library as a product in its own right. The Tax Library is a structured, browsable copy of federal and state statutes, regulations and guidance, navigable from title to chapter to section, with autocomplete so a section number does not have to be recalled from memory. Any provision has a shareable link. Alongside the research chat sit a SALT Matrix for state-by-state questions, memo and client email drafting, and client-scoped workspaces.

The content underneath is public-domain primary law rather than a licensed editorial library, and Marble is straightforward about that: statutes, regulations, official filing instructions and guidance across all 50 states. That is the honest boundary of the product. It will show what the code says and where the rule lives. It will not hand over a Thomson Reuters or CCH analyst's explanation of an unsettled position, because it does not have one to give. Currency looks real rather than claimed. The company's own editorial covers 2026 QBI thresholds and phase-in ranges under the One Big Beautiful Bill Act, which is the kind of specificity a stale index does not produce.

The gap worth knowing about is state depth. The Tax Library page lists live coverage for a set of states and shows a request option against others, so coverage is uneven rather than uniform across the 50 states the marketing claims. Nothing on the site describes how the assistant behaves when authority is genuinely unclear, whether it hedges, declines, or answers anyway, and that behaviour is the difference between a research tool and a liability. Anyone trialling it should spend the 14 days asking questions with no clean answer and watching what comes back.

Against TaxGPT, Marble wins on transparency: a published $600 per user per year, a free tier with limited daily chats, a 14-day trial with no card, and a SOC 2 Type II report handed to Pro subscribers, versus TaxGPT's demo-only pricing. Against Checkpoint or CCH AnswerConnect it is a fraction of the price and a fraction of the editorial depth, which is the trade every firm in this category is really making.

Moved up from one to watch to strong option. The evidence for the move is concrete rather than atmospheric: SOC 2 Type II with annual independent audits, published per-seat pricing, single sign-on on every plan including the free one, a full-text library shipped as a browsable product, and distribution through the BDO Alliance USA network and a preferred-platform arrangement with the National Association of Enrolled Agents. No customer count is published and the company does not disclose a founding date, so install base remains unverified. But the buying signals a small firm can actually check all point the same way.