The short answer
There is no single right account structure for every couple. A joint household account can make shared bills easier, while separate personal accounts can preserve autonomy. For many couples, a three-account system works well: one shared account and one personal account each.
The account is not the difficult part. The difficult part is agreeing what is shared, what remains personal and what each person needs to know.
A joint account can simplify rent or mortgage payments, utilities, groceries, childcare and other household commitments. It can also give both partners visibility over the cost of running the home.
But full financial merging does not suit everyone. Different incomes, previous relationships, debt, caring responsibilities and different attitudes to spending can all affect what feels fair.
Questions to agree first
Start with a household account for agreed bills and a standing order from each partner. Review the amount after two or three months. The system should make the money conversation easier, not replace it.