My question is simple: do writers need a business bank account? Or can they use a regular account for saving and declaring tax on their earnings?

Further, do writers need to declares themselves a private company?

My question is simple: do writers need a business bank account? Or can they use a regular account for saving and declaring tax on their earnings?

Further, do writers need to declares themselves a private company?

Edit: UK/England based, for the purposes of writing as a secondary income rather than a primary (though how primary incomes compares to secondary would also be interesting to know).