The requirement is a letter from your Embassy - so what they will accept will the the main thing. Once that is obtained they might want to see proof or incoming funds but that is likely to vary from officer to place to time.

If the wife has tax paid income of 40k per month from employment of some type that will work. Just paying the tax itself might not. But again it is likely to be a local call.

The wife will never have a "real" job or it is highly unlikely but she does and will own assets (provided by me). I'm going through the various allowances and what have you to see which way works best. I am concious of the fact that whilst today it is 40k per month, it may rise and rise significantly and the only hope would be to be grandfathered. Look at the retirement amount. I believe 200k to 400k to 800k or something ?

Anyway, I roughly calculate the tax on an employed income of 40k below (no social contributions included, nor investment allowances)

Employment

Monthly income 40,000

Annual income 480,000

Deductions (60,000)

Allowances

Personal (30,000)

Married (30,000)

Baby (15,000)

Life assurance (50,000)

Taxable income 295,000

Tax 19,500

Per month 1,625

To do it via the own business route with allowances of 85% of turnover, the figures look like this:

Business

Income 3,200,000

85% deductions (2,720,000)

Allowances

Personal (30,000)

Married (30,000)

Baby (15,000)

Life assurance (50,000)

Taxable income 355,000

Tax 25,500

I will happily stand corrected if my maths are way off but I have used what I have found so far and it is a clear winner for the employment route.