If you can't find your purchase date and price, check your old tax filings for clues. Thinkstock By Kimberly Lankford, Contributing Editor From Kiplinger's Personal Finance, April 2015 I bought shares of GTE nearly 50 years ago, and it eventually became Verizon stock. I’m trying to figure out what the cost basis would be if I sell the shares, but I am having a hard time because of the splits, mergers and spin-offs. -- R.M., College Park, Md.See Also: Biggest Mistakes Investors Make Verizon has a calculator on its site that can help you figure out your basis if you originally had GTE, Bell Atlantic, NYNEX or Contel shares (Bell Atlantic and NYNEX shares from the AT&T divestiture require a trickier series of calculations). Many companies’ investor services sites have worksheets or helpful information. A database such as Wolters Kluwer’s Capital Changes, available in libraries, can also help. Try to find a record of the purchase date and price. If you can’t track that down, ask the company’s investor services or your brokerage firm for information. Brokers must now keep cost-basis data for stocks bought in 2011 or later, but most have older records. You might also find clues in your tax files—for example, showing when you started paying taxes on the dividends. Another option is to give the shares to charity. You’ll get a tax deduction for the current value of your Verizon stock and never have to figure out the basis. Got a question? Ask Kim at email@example.com.