Example: A plumber, who is a resident of Rhode Island, carries on his business from an office in Danielson, Connecticut. He has maintenance contracts with housing authorities in the Worcester, Massachusetts area which require him to regularly perform his services at various locations in and around Worcester. Assume that this taxpayer allocated, on the basis of separate books and records, the income derived from his plumbing business on his Connecticut nonresident return as follows: 60% to Connecticut and 40% to Massachusetts. Therefore, on his Massachusetts return, this taxpayer shall also allocate 60% of this income to Connecticut and 40% to Massachusetts, since Massachusetts permits allocation on the basis of separate books and records.
Conn. Agencies Regs. § 12-711(c)-4