Tax Document Parsing in 2026: 1099s, W-2s, and 1040s at Scale

Tax season hits different when you're processing thousands of documents for mortgage underwriting, income verification, or financial analysis. Here's what I learned building parsers for the big three tax documents. The Problem with Tax Documents Every tax document looks simple until you try to parse it at scale: W-2s : Employers use different software (ADP, Gusto, Paychex, QuickBooks), each with slightly different layouts. Box positions drift. Multi-state filers get multiple copies. 1099s : There are literally 20+ variants (1099-INT, 1099-DIV, 1099-NEC, 1099-MISC, 1099-K...). Each has different fields. Brokerages love adding supplemental pages. 1040s : The IRS form itself is standardized, but schedules vary wildly. A simple return might be 2 pages. A complex one with K-1s and foreign accounts? 50+ pages. What Actually Works After processing millions of tax documents, here's the stack that scales: 1. Vision Models Beat Traditional OCR Forget Tesseract for tax docs. Vision models (GPT-4o