In 2003, Fannie Mae and Freddie Mac, two government-sponsored entities that play a critical role in the U.S. housing market, made significant accounting errors related to the way they reported income and expenses. The mistake was linked to the incorrect application of accounting methods for hedging activities—particularly how they handled derivatives used to manage interest rate risk. Fannie Mae, in particular, miscalculated the timing of its expenses related to these derivatives, leading to an overstatement of its earnings. This error ultimately resulted in a restatement of financial results and an SEC investigation.

In 2012, JPMorgan Chase incurred a massive trading loss of over $6 billion, which was initially attributed to a mistake in accounting. The loss stemmed from a complex financial strategy involving credit default swaps (CDS), but a key accounting mistake was made when tracking the position in the spreadsheet used by the traders. A manual error occurred when inputting data into the spreadsheet, leading to the inaccurate reporting of the bank's exposure to risk. This error significantly overstated the bank's risk management capabilities and was not caught until it had spiraled into a huge loss. 

Knight Capital Group, a major U.S. financial services firm, suffered a catastrophic loss of $440 million in just 45 minutes due to an accounting-related mistake in its trading software. The error occurred when the company improperly installed new software meant to improve its trading algorithms. A coding mistake triggered a massive number of erroneous trades, leading to unintended purchases and sales of stocks. This glitch, which was technically a software error but had the same impact as an accounting mistake, caused significant financial losses for Knight Capital.