"For me to try to verify that they had calculated it correctly, I couldn't do it without the help of another tax expert," said Rosenthal, a lawyer who had worked on the issue while in private practice.
The way financial companies are sending information on cost basis to investors isn't standardized, said Kathy Pickering, executive director of the Tax Institute and vice president of government relations at H&R Block Inc. The Kansas City, Missouri-based company is the largest U.S. tax preparer.
Some brokers are providing cost basis information on shares purchased before 2011 while others are providing it for those bought and sold last year, so investors looking at different statements may be confused or have trouble finding the information they need for their return.
The sales and basis information, reported on Form 1099-B, were required to be filed by Feb. 15, and some brokers received extensions from that date.
The flurry of late forms may cause some taxpayers to file for extensions, said Abe Schneier, senior technical manager at the American Institute of Certified Public Accountants in Washington.
Customers who used TurboTax and elected to have tax software electronically import their brokerage account information had the 1099-B information on their cost basis pulled in from financial companies for them, said Bob Meighan, a vice president at Intuit Inc.'s TurboTax.
"They're sort of being shielded from all the complexity that's going on behind the scenes," Meighan said. "We did have to write quite a bit of code to accommodate the new 8949 and all the exceptions that form is designed to handle."