Your basis is generally the cost of the investment less any prior nondividend distributions received. Once you enter the basis in TaxAct, the program will determine if there is a gain to report and it will report it on Form 8949.
The most common kinds of distributions are:
Nondividend Distributions - Report any amounts in excess of your basis in your mutual fund shares on Form 8949. Use Part II if you held the shares more than 1 year. Use Part I if you held your mutual fund shares 1 year or less. For details on Form 8949, see Reporting Capital Gains and Losses in chapter 4, and the Instructions for Form 8949.
Per IRS Publication 550, Investment Income and Expenses, Page 20:
A nondividend distribution is a distribution that is not paid out of the earnings and profits of a corporation or a mutual fund. You should receive a Form 1099-DIV or other statement showing you the nondividend distribution. On Form 1099-DIV, a nondividend distribution will be shown in box 3. If you do not receive such a statement, you report the distribution as an ordinary dividend.