X.TAX API
X.TAX ships a public developers portal with OAuth 2.0 client credentials, free sandbox keys, and filings endpoints for 1065, 1120, and 1120-S. Production still runs through a Developer Access approval step, and webhooks, SDKs, and versioning policy are absent.
Frequently asked questions
X.TAX scores C+ on Supergood's API Report Card. X.TAX ships a public developers portal with OAuth 2.0 client credentials, free sandbox keys, and filings endpoints for 1065, 1120, and 1120-S. Production still runs through a Developer Access approval step, and webhooks, SDKs, and versioning policy are absent.
X.TAX has an official API, but teams routinely hit its limits: gated access, partial coverage, or paid tiers. Most end up supplementing it with exports or an unofficial API layer like Supergood. Site terms may apply to any integration approach, and how they apply is a determination each team makes for itself.
X.TAX is an AI-first business tax platform that prepares and e-files federal and state returns for LLCs, S-Corps, C-Corps, and partnerships, covering Forms 1065, 1120, 1120-S, extensions, and state returns.
Finance, specifically business tax compliance for growth stage startups and small businesses that file entity returns, plus the accounting software vendors and fintech products that want to embed filing rather than build tax logic. Finance teams connect QuickBooks Online or Xero, let the platform pull income, expense, and balance sheet data, review the automatically mapped return, and then e-file the federal return with per state returns added as needed, with CPA and EA assistance available for a fee.
X.TAX is an early stage Austin based platform that launched publicly after roughly a year of quiet operation, and no customer counts, logos, or market share figures are published in any of the sources reviewed.
The system holds entity level tax filings and the financial data behind them: income statement and balance sheet figures imported from QuickBooks and Xero, the mapped form data for 1065, 1120, and 1120-S returns, extensions, state returns, validation results, and transmission status for each filing.
The platform is new.
Common alternatives include CCH ProSystem fx Suite, TaxPrep, Taxfyle, Bloomberg Tax. Graded alternatives appear under "More from the report card" below.
Supergood's grades measure one thing: can a customer's engineering team get their own data out programmatically? Supergood checks six things (whether a real API exists, how access is gated, data coverage, auth quality, docs and developer experience, and stability) and rolls them into a letter grade. Supergood re-verifies grades, and they only move on evidence.
Not that we could find. As of August 2026 there is no official X.TAX MCP server in any public registry, and no maintained community server we're aware of. We re-verify this periodically — report an inaccuracy below if we missed one.
Not natively. X.TAX doesn't publish an MCP server, so MCP clients like Claude, Cursor, and Codex have nothing to connect to out of the box. If that changes, this page will reflect it.