Buy expert domain data from professional firms

What is expert domain data?

Expert domain data is the record of skilled professional work, kept by the firms that did it. It includes closed matter files at law firms, tax returns and workpapers at accountancy practices, project records and drawings at construction companies, and de-identified clinical notes at medical practices.

Labs buy it to teach models complete professional tasks, from instruction to finished output. MIT Technology Review reported in October 2026 that Surge AI builds reinforcement learning gyms where agents practice tasks such as drafting appellate briefs.

How much do AI companies pay for expert domain data?

AI companies pay from tens of thousands of dollars to over $1 million per firm for expert domain data, depending on the profession and the size of the archive. Mercor's published listings, compiled by ddiy.co in October 2026, give these company payouts.

These are payouts to the firms supplying data, not buyer prices, and each range spans small and large firms. The Next Web reported that micro1 has committed $1bn over 12 months to buying and licensing operational company data, a sign of the competition for good archives.

Firms on the supply side can read our pages for law firms, accounting and tax firms and medical practices.

Expert domain data carries professional duties as well as privacy law. Client files sit inside a relationship governed by confidentiality, and often by contract terms that restrict reuse.

Our seller vetting covers contract restrictions, the privacy notice in force when the records were made and the de-identification method, so shortlisted firms have already cleared those checks. You still need independent legal advice on your own intended use.

• Medical records: HIPAA allows de-identification by expert determination or by removing 18 listed identifiers under 45 CFR 164.514, and HHS says de-identified health information is no longer protected health information
• Tax files: US preparers face IRC Section 7216, which prohibits knowingly or recklessly disclosing or using tax return information
• Legal files: attorney-client privilege and client confidentiality
• Engineering drawings: client ownership of designs under some services contracts

If you are buying UK or EU records, client files are also personal data under UK GDPR or EU GDPR unless anonymized, and health records are special category data.

How should expert domain data be delivered?

Expert domain data should be delivered as complete files grouped by matter, engagement or project, with documents in native formats where possible and a manifest listing each file's type, date and role in the workflow. Drafts add value: Mercor's consulting listing, for example, covers client deliverables and the drafts behind them.

Ask for a short note of each file's outcome, such as the matter result or the audit opinion, so the record can be turned into tasks with known answers.

What should you check before buying expert domain data?

Before buying expert domain data, check that each file runs from instruction to outcome and that the authors held the relevant qualifications. Our guide to data provenance lists the records that prove where each file came from.

Ask how clients and counterparties were de-identified, who reviewed the result and whether any files were excluded for privilege or regulation. Every seller we shortlist passes our eight-point vetting standard. Book a free consultation to source vetted professional archives.