Philip Rooney 48, of Lanarkshire, Scotland, faces three counts of causing death by dangerous driving.
The London-to-Aberdeen National Express coach overturned on the M4/M25 slip road on 3 January. Two people died soon after and a third died on 1 July.
Mr Rooney is due to appear before Reading magistrates on 31 July.
Christina Toner, 76, from Dundee, Scotland, and 30-year-old Yi Di Lin, a Chinese national, died in the crash.
John Carruthers, 78, of Chertsey, Surrey, died six months later in hospital on 1 July,