I'm sorry if this is a strange or incorrect question. I'm reading a Japanese novel about Toyotomi Hideyoshi, and I'm getting the impression that commoners didn't use last names in the Edo period.
The Early Meiji Era.
On October 13th, 1870 the 平民苗字許可令 was passed, which allowed non-nobles to use a family name.
On February 13th, 1875 the 平民苗字必称義務令 was passed, which made it mandatory for everyone to use a last name.
At this point everyone had to have a family name. It's generally accepted that the massive numbers of certain family names (i.e. 田中、鈴木、川本、etc.) comes from this period, when peasants suddenly had to choose a name for themselves.