I had stock in a company for 17 years. I transferred from a brokerage house to another after buying the shares. The company had a Cash Merger and my shares were cashed out. The value on my 1099-B for the "Cost Basis" is blank. I only see the value of the transaction. What do I enter on my 8949 form (which goes to my Schedule D) for the Cost Basis?

Your cost basis is the amount you paid for the stock 17 years ago - as with all investments you should have kept records of what you paid. Brokerages didn't start reporting cost basis until just a few years ago, so stocks held longer than that typically won't have cost basis reported on 1099-B (unless you've separately informed the brokerage of your cost basis).

If you have no records but remember when you purchased the stock, it should be possible to look up what the market price was, and you can use that for your cost basis.

You may also want to check out the website of the merged company; they often cover the basis of the pre-merger stocks in their Investor Services section of the website.