Additive
GenAI extraction that turns Schedule K-1 and related PDF tax documents into structured Excel workpapers.
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About Additive
Additive is a generative AI document extraction tool that converts pass-through entity tax documents into structured data. It handles Schedule K-1 forms from 1065, 8865, 1041 and 1120-S filings, along with K-3, 199A, 926, 8621, UBTI and 65 state forms, and extracts footnotes and supplemental statements rather than stopping at the face of the form.
Founded in San Francisco in 2023, Additive was acquired by Thomson Reuters in September 2025 and now sits alongside the SurePrep and CoCounsel Tax product lines. The company states SOC 2 Type 2 compliance and cites accuracy of over 99% on characters of income and over 95% of footnotes, both of which are its own figures. Crowe adopted the product in May 2026.
It is positioned for accountants preparing returns in the asset and wealth management space, and is marketed at Top 20 firms, family offices and private wealth management groups rather than at small practices.
Key Features
- K-1, K-3, 199A, 926, 8621 and UBTI extraction across 65 state forms
- Footnote and supplemental statement extraction, not just the form face
- Excel add-in plus API, with PDF, JSON and Excel workpaper export
- SOC 2 Type 2 attested, used by Big 4 and Top 20 firms
Our in-depth review
Additive is a K-1 extraction tool built for the asset and wealth management corner of tax preparation, now owned by Thomson Reuters following a September 2025 acquisition. Its scope is deliberately narrow.
What it does well. The narrowness is the point. It covers K-1, K-3, 199A, 926, 8621, UBTI and 65 state forms, and it extracts footnotes rather than stopping at the face of the form, which is where most of the manual effort actually sits. Output lands as Excel workpapers, JSON or PDF, and there is an Excel add-in plus an API, so it fits existing review habits instead of demanding new ones. SOC 2 Type 2 attestation is in place, and Thomson Reuters ownership brings a documented SurePrep integration.
Where it falls short. The accuracy figures, over 99% on characters of income and over 95% of footnotes, are the vendor's own and carry no published independent verification. Pricing is not disclosed anywhere, and every route to the product now runs through a Thomson Reuters demo form, so smaller firms will struggle to get a straight answer on cost. The testimonials on the site are anonymised by firm tier rather than named. It does one document family and nothing else.
Best for. Mid-sized and large firms with heavy pass-through workloads, plus family offices and private wealth groups that lose weeks to K-1 season every year.
Verdict. The strongest dedicated K-1 extraction option on the market, provided your volume justifies an undisclosed enterprise price.
At a glance
- Category
- Tax prep
- Best for
- 50+ practice
- Editor's score
- 4.5 / 5
- Pricing
- Pricing is not published. Access is demo-led through Thomson Reuters, so expect enterprise quote-based pricing.
- Last verified
- 2026-09-13
Best-in-class K-1 extraction for high-volume firms, held back only by opaque enterprise pricing.
Integrations
- Microsoft Excel
- Thomson Reuters SurePrep
- API
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