In 1727, Costa brought an action against the Russia Company, which refused to admit him to membership on the ground of his being a Jew.
The attorney-general decided that he must be admitted, whereupon the company petitioned Parliament to modify the former's charter so as to give it the right of refusal.
He married Leonora (Rachel) Mendes, sister of Fernandez (Fernando) Mendes, the Marrano physician of King John IV of Portugal.
[1] Catherine da Costa made the water-colour portrait of her father which now hangs in the vestry of the Bevis Marks Synagogue.
[2] Their children included Sarah (Simha) Mendes da Costa who married Ephraim Lópes Pereira d'Aguilar, 2nd Baron d'Aguilar.