August 6th , 1920
In response to the expulsions of Catholic workers and the violence in Belfast and other northern towns, northern Sinn Féin members called for the boycott of Unionist-owned businesses and banks in the city. Despite some opposition, the Dáil and its cabinet approved the boycott in August 1920, imposing a boycott of goods from Belfast and a withdrawal of funds from Belfast-based banks.
In January 1921, the Dáil agreed to support the boycott more fully, providing 35,000 pounds to the campaign. Joseph MacDonagh (brother of executed 1916 Easter Rising leader Thomas MacDonagh) oversaw the implementation of the boycott, by May 1921 there were 360 Belfast Boycott committees throughout Ireland, but it was enforced intermittently.