Unless the lower of cost or market or mark to market methods are used for tax purposes, the owner of stock in a corporation cannot deduct from gross income a loss due to shrinkage in value of such stock through fluctuations in the market or otherwise until the stock is sold. The allowable loss is the amount realized when the stock is sold. If the stock of a corporation becomes worthless, the stock's tax basis may be deducted in the tax year in which the stock became worthless.
4.26 Ark. Code R. 51-424(a)(1)