The legal rights you have as a partner depend heavily on whether you are married or living together. On the whole, you will have more rights if you are married compared to living together.
Living together: You can make decisions formally by drawing up a cohabitation contract or living together agreement. This can outline any rights and obligations each side of the party have.
Marriage: When a married couple have a joint bank account, the money is jointly owned regardless of who put it into the account. On the death of a partner, the account immediately becomes the property of the surviving partner.