We have a joint account for bills and both my wife and myself have a standing order to transfer a set amount of our wages into it every month. We calculated the rough amount needed to cover monthly bills, then added another 20% on top. This money slowly builds up and provides an extra pot of cash for unforeseen large purchases, the occasional holiday etc. Once that account gets to a certain level, we transfer a chunk into a savings account and this has also grown enough to cover us in case of job loss etc (or really big purchases). It works well for us.