Country X levies corporate income tax at a rate of 25% and charges income tax on all profits irrespective of whether they are distributed by way of dividend. Country Y levies corporate income tax at a rate of 20%.

A, who is resident in Country X, pays a divided to B, who is resident in Country Y. B is required to pay corporate income tax on the dividend received from A, but a deduction can be made for the tax suffered on this dividend restricted to a rate of 20%.

Which method of relief for foreign tax does this describe?