Ameritrade, the US online broker, last night agreed to buy rival TD Waterhouse USA in a transaction that values the Toronto-Dominion Bank unit at about $2.25bn (€1.9bn). The combined firm will become the biggest online broker by volume of trades.

Citigroup is advising Ameritrade, while Goldman Sachs and TD Securities are advising TD Bank Financial Group on the sale of its US brokerage business.