Thanks Brendan, this makes sense. We absolutely intend to have a legal agreement written up but we were thinking along the lines of saying that should we split up and sell the house/one person buy the other out, the formula used to calculate who gets how much/owes how much would reflect the larger deposit put in by one party. Obviously if the house reduces in value, a proportionate percentage of that. The reason why we want to have equal ownership of the house is so that we can have joint tenancy without the need for a will or the need to pay inheritance tax should one of us die.