Sky Sports understands the 27-year-old is edging closer to a return to London and he is scheduled to hold talks with Martin Jol on Thursday evening to finalise the switch.
Richardson has been given permission to speak with the Cottagers after the Black Cats reluctantly accepted a bid for the midfielder.
Martin O'Neill had wanted the former Manchester United starlet to remain at the Stadium of Light but was sympathetic to the player's pleas to return to the capital for family reasons.
Armed with the ?15 million from the sale of Mousa Dembele to Tottenham, Martin Jol now looks set to splurge the cash.
Richardson is likely to join Dimitar Berbatov in west London after he successfully completed a medical ahead of his potential ?4 million transfer.
Clint Dempsey's future at the club still remains uncertain with Liverpool and Sunderland both vying for his signature before the transfer window closes.
