A split is a corporate action in which a company's existing shares are divided into multiple shares. Although the number of shares outstanding increases by a specific multiple, the total dollar value of the shares remains the same compared to pre-split amounts.
For example, in 2011, Citigroup (C) conducted a 10:1 reverse split, each stockholder had a reduction in the number of issued shares by a ratio of 10:1
Updating Positions Effected by a Stock Split
Step 1: Navigate to the Audit / Corporate Actions page.
Step 2: Enter the Symbol, Ratio, Action Date, and New Symbol (if necessary).
Step 3: Preview the results to view all open positions on the action date and click save.