Bank of America Corp. and Citigroup Inc. incorrectly hid from investors billions of dollars of their debt, similar to what Lehman Brothers Holdings Inc. did to obscure its level of risk, company documents show.

In recent filings with regulators, the two big banks disclosed that over the past three years, they at times erroneously classified some short-term repurchase agreements, or "repos," as sales when they should have been classified as borrowings. Though the classifications involved billions of dollars, they represented...