How do I calculate the average basis for the sale of mutual fund shares?

To figure your gain or loss using an average basis, you must have acquired the shares at various times and prices.

To calculate average basis:

  • Add up the cost of all the shares you own in the mutual fund.
  • Divide that result by the total number of shares you own. This gives you your average per share.
  • Multiply the average per share by the number of shares sold.

You may no longer use the double-category method for figuring your average basis. If you were using that method for shares acquired before April 1, 2011 and you sell, exchange, or otherwise dispose of those shares on or after April 1, 2011, you must figure the average basis of those shares by averaging together all identical shares in the account on April 1, 2011, without regard for the holding period.

If you wish to use the average basis to figure the gain on the sale of mutual fund shares, you must elect to do so. To choose the election, there are two separate processes for making the election for average basis method for covered and noncovered securities. See Publication 550, Investment Income and Expenses (Including Capital Gains and Losses) for information on how to make these elections.