It depends. If the lines of work are related (different sales products, for example), report those activities on one Schedule C. But if your businesses are essentially separate (sales and consulting, for example), you may prefer reporting those activities on separate Schedules C. This would apply if your lines of work began in different years, or if they don't share assets. You can have as many businesses as you like on your return. The IRS is mostly concerned that you report all your business income.