Hey modensane, welcome to the forum. I'm not an expert but I'm sure one will be along shortly to answer you question. You are in a great place for advice and support so hang on in there for an answer. Viki X
If you are both going BR, then you need to cpmplete two SOA's. The general rule of thumb is to put the full household expenditure on both, with the partner's monthly contribution making up any shortfall.