Mark,

I placed a contract for 10 GE covered callsSP40 Sept.Now I want to buy them back before expiration. I'm afraid my stock will be called away,

and I don't want to pay capital gains.

CK

Hello CK,

1) If you want to repurchase those calls, simply enter an order to buy (to close) 10 GE Sep 40 calls.

2) You can enter a market order to be certain you buy them, but that is usually a bad idea.  Enter a limit order for the price you are willing to pay.

3) I'm not telling you what to do, but there is no chance that your stock will be 'called away' unless GE is above 40 when expiration arrives.  It's very unlikely that you would be assigned earlier.  The only exception occurs right before the stock goes ex-dividend, when you may be assigned, if GE is significantly above 40.  Thus, you can wait before buying those calls. 

4) On the other hand, if you are happy to own your GE stock unhedged and (hopefully) take a profit on those calls at the same time, then by all mean, buy them back.

Mark

--
Mark D. Wolfinger
The Rookie's Guide to Options:
The Beginner's Handbook of Trading Equity Options