emigration from Kilkenny to England in the 19th century

[Birkenhead]

my great, great grandfather John Cunningham, left Kilkenny in the early part of the 19th century to live in Liverpool, then in Birkenhead Cheshire where he lived and died. Can anyone tell me of the documentation ( if any) needed or the process followed in order to leave Ireland.?
Jeanette McIntyre

[aghadowey]

Ireland was part of the U.K. so no records were kept of people travelling between Ireland and England, Scotland and Wales.