In general, any capital gains you have can be offset by any capital losses you have.
If your business is a sole proprietorship which you decide to sell 20% of, then that sole proprietorship has now become a partnership, provided that the entire business remains intact. You will need to register with your state and or county as such and obtain an new employer identication number. If the buyer of the 20% is not going to be a part of the business and separates everything from your business, you will not need to change your business structure.
If the business is already a partnership, there is no change in structure needed when you sell 20% of your holdings to another partner or potential partner. To determine your capital gain, you will need to deduct 20% of your basis prior to sale from the amount of proceeds you receive. The net amount can then be used to offset any capital losses you have accrued.
