Seems straight forward but I'm having issues - in short I purchased a security in '99 that reverse split 1:1000 then reverse split again 1:75 and was delisted in 2007 so I reported it is a worthless security to get it off the books this year (don't ask why it took so long). The rub is I only had 500 shares at the time of the split but even though each of the splits would have put me into fractions I still received 1 full share. Going through the calculations my basis is through the roof and doesn't seem right. Anybody have any suggstions on how to accurately determine my loss?

In summary:
bought 1000 share
sold 500 share
reverse split 1:1000 giving me 1 share
reverse split 1:75 giving me 1 share
delisted 1 share

Any help would be much appreciated

Reverse split is a reduction in the number of a corp's shares outstanding that increases the par value of its stock or its earnings per share. A reverse stock split is a corporate action in which a company reduces the number of shares it has outstanding by a set multiple. This is the opposite of a stock split, in which a company increases its outstanding shares by a set multiple. For example, if a company announces a reverse stock split of 1:1000, this means that once the split occurs, investors will receive one share for every 1000 shares they own. In other words, if the company has 100 million shares before the split, this number would be reduced to 100,000 after the split. As in a regular stock split, a reverse split causes no actual change in the value of the company because the share price also changes. However, some investors can be cashed out of their positions if they hold a small number of shares. For example, if an investor holds 500 shares of a company that splits 1:1000, that person would be left with only half a share, so the company would simply pay that investor the value of the 500 shares. Reverse stock splits are often seen as negative corporate actions because they are a tactic used by companies that have seen their share prices fall into the $1 range and, therefore, run the risk of being delisted from stock exchanges that have minimum share price rules. For example, if a company is listed on the Nasdaq and its shares fall below $1, it runs the risk of being delisted; companies sometimes reverse split to increase share price, allowing them to continue to trade on a reputable stock exchange. If a company has been delisted, it is no longer trading on a major exchange, but the owners of the company shares are not stripped of their status as owners. However, delisting often results in a significant or total devaluing of a company's share value. Therefore, although a shareholder's ownership of a company does not decrease after a company is delisted, that ownership may become worth much less or, in some cases, it may lose its entire value. I guess you can get some professional help/advice form your broker.