Expenses of sales and commissions would be added to your original cost basis to arrive at the amount to enter for Cost or other basis. The TaxAct program does not ask for these items separately. Therefore, you will want to keep detailed records to support this entry.
Per IRS Publication 550 Investment Income and Expenses, page 65:
Form 1099-B transactions. If you sold property, such as stocks, bonds, or certain commodities, through a broker, you should receive Form 1099-B from the broker. Use the Form 1099-B to complete Form 8949 and/or Schedule D (Form 1040 or 1040-SR).
If you received a Form 1099-B for a transaction, you usually report the transaction on Form 8949. Report the proceeds shown in box 1d of Form 1099-B in column (d) of either Part I or Part II of Form 8949, whichever applies.
Include in column (g) any selling expenses or option premiums not reflected in box 1d or box 1e of Form 1099-B. If you include a selling expense in column (g), enter “E” in column (f).
Enter the basis shown in box 1e in column (e). If the basis shown on Form 1099-B is not correct, see the table How To Complete Form 8949, Columns (f) and (g), in the Instructions for Form 8949 for the adjustment you must make. If no basis is shown on Form 1099-B, enter the correct basis of the property in column (e). See the instructions for Form 1099-B, Form 8949, and Schedule D (Form 1040 or 1040-SR) for more information.
[Please see this section of the publication for examples.]
To make this adjustment for expenses of sale in the TaxAct program:
If, on the screen titled Investment Sales - Transaction Details, you entered the GROSS sales proceeds instead of the NET sales proceeds, then you will need to make an adjustment. On the screen titled Investment Sales - Adjustment Code(s), select Code "O" from the drop down list. On the following screen, you will enter the amount of the sale expenses as a negative adjustment. This will increase your overall basis, thus reducing the gain (or increasing the loss).
Note. Any link in the information above is updated each year automatically and will take you to the most recent IRS version of the document at the time it is accessed.