It starts with your parents cost of the shares which would be on their balance sheet a the time shares were created. Once the shares are gifted to you, the cost basis for you is the same as it was in their hand. Only they can give you the cost basis at that time, that basis carries to every stock exchange going forward until sold.
There are two options, one is to do the research and if they had a tax professional do their books and tax returns, they may have an answer. If not, the other option is to put zero in for the cost basis. You can arrive at a reasonable amount by using the capital contributed by your parents at the time the stock was created.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
