What to do When You Can't Find a Stock's Cost Basis Howard Hook, CFP®, CPA, quoted in NJMoneyHelp on July 6, 2015The Question: I have some stocks that I’ve owned for more than 20 years. I don’t know the cost basis of all, but I plan to sell to pay college tuition bills for my son. What do I do? The Answer: Recordkeeping for your investments will save you headaches likes these down the road, but we know there are times when needed documents do a disappearing act. Not knowing the cost basis of investments is a very common problem many taxpayers face, said Howard Hook, a certified financial planner and certified public accountant with EKS Associates in Pronceton. “Even if you know the date you purchased the stock, there could be stock splits, corporate reorganizations or mergers that all will affect the cost basis,” Hook said. “For dividend-paying stock owned in a brokerage account there also could be reinvested dividends that affect the cost basis, which until only recently was required to be tracked by brokerage firms.” The good news is that with a little research, you can probably find the information you need. Hook said many companies post information on their web sites listing the splits and reorganizations. Some even have calculators for determining the cost. But for that to work, you will need to know the purchase date, Hook said. “Unfortunately, absent of that, you may not be able to accurately calculate the cost basis,” he said. But you’re going to want to try — and try hard — or it will cost you. “The tax law states that if you have no documentation, then the basis is zero,” said Gail Rosen, a Martinsville-based certified public accountant. When you do find a cost basis to use, make sure you understand which shares you want to sell first. And if the stock was inherited, you may have an easy time finding the cost basis.