If the wife isn't bringing in enough to pay tax you should be paying her the difference, or if no income at at all you should be paying her in the region of £186 per week as this would mean you losing this amount against your returns, and also gives the wife some money, coz you love her 😘
This way no tax is paid and ni is about £2-3
Yes in theory the wife is an employee so insurance required, or could be done as a partner or the wife could be self employed, and do her tax returns based on not earning enough to pay tax and also submit tax returns and deductions.