Company secretary and director can be the same person, at least it is in my business. The ideal payment for a sole director who doesn't have another income source is an annual wage of £7,696 (this incurs no tax or NI liability for the employee or employer) then the rest of your payments are dividends. The first £32,010 of dividends after the above salary incur a personal tax element of 10% which is retained by the company called a dividend tax credit. Your limited company cannot pay out more in dividends than the ***ulative profit it has made since it has started, this is illegal.
Dividends are paid from profits which have either been taxed for corporation tax (previous financial years) or are due to be (current year). The corporation tax rate is currently 20%. As the company keeps the 10% dividend tax credit it effectively pays 10% tax on the dividend payment.
In practise, if I want to pay myself £27,000 of dividends plus the £7,696 salary, the company on paper pays £30,000 of dividends (gross). In practise, it pays you £27,000 and it keeps £3,000 itself. Your self assessment tax return would show you have been paid £30,000 of dividends plus the £7,696 salary. You have therefore earned £37,696 and paid just £3,000 tax. The company will have paid £1,460.80p corporation tax on the money it's earned less the loss due to the salary. Total tax liability between self employed and the company is £4,460.80p
Contrast this with a self employed setup, you will pay tax on all profits. Let's assume the same setup, i.e. £37,696 of profits: -
Tax at 20% on all earnings over £9,440 = £5,651.52p
NI at 12% on all earnings over £7,755 = £3,592.92p
TOTAL tax and NI on earnings = £9,244.44p
So in this scenario you would pay an additional £4783.64p each year for the privilege of being a sole trader.
I don't think there is any scenario that I can think of where it is better to be a sole trader from a pure tax perspective.
I have made a couple of minor simplifications to keep the scenario straightforward above but the figures are 99% accurate. I hope this helps to clear up any confusion on the subject. It may make people more confused, in which case I am sorry