If you set up and operate an unincorporated business by yourself, you are a sole proprietor. If you set up a limited liability company (LLC) to operate your business, you are still considered a sole proprietor unless you elect to treat the LLC as a corporation.
Corporation
If you set up your business as a corporation, even if you own most or all of the stock, your income as an employee or officer of the corporation is not subject to SE tax.
S corporation
If you are a shareholder in an S corporation, your share of the corporation’s earnings are not subject to SE tax. If you perform substantial services, you are an employee of the S corporation, and you are subject to withholding of social security and Medicare taxes, and are not subject to the self-employment tax.
Partnerships
If you are a general partner in a partnership that carries on a trade or business, you are considered self-employed. If you are a limited partner; that is, you have an interest in the partnership but do not actively participate in its management and operations, you are generally not considered to be self-employed.
If you and your spouse operate a business as a partnership, you should report your business income and expenses on Form 1065, U.S. Return of Partnership Income, and attach separate Schedules K-1 showing each partner’s share of the earnings. Each spouse must must then report his or her share of the partnership earnings on Form 1040 and file a separate Schedule SE to report self-employment tax.
However, if one spouse is contracted as an employee of the other, rather than being treated as a partner, you must withhold and pay social security and Medicare taxes for him or her.