Depending on when you’re going to use it next, leftover tofu can either be stored in the fridge or the freezer.
If you plan to eat the tofu in the next week, place the leftover block in an air-tight container and cover with cool water. Changing the water regularly will keep the tofu fresh.
For freezing, cut the tofu into squares, place on a tray with baking paper and pop in the freezer. Once frozen, transfer to a container. Tofu should last a few months in the freezer.