The IRS recently advised a husband and wife, who together owned an unincorporated business, that their business would be treated as a partnership unless the couple elected for it to be disregarded (Private Letter Ruling 201411035).
The tax law defines a partnership to include any multi-owner unincorporated organization through or by means of which a business, financial operation or venture is carried on. Regulations allow certain unincorporated organizations to elect out of partnership treatment.
In either case, each spouse is responsible for paying any required self-employment tax on his or her net earnings from self-employment.