Explain how the McCanns would have paid corporation tax.
It has no relevance to the OP, in fact this thread has been pretty much off topic since about page 2 I merely joined in "In the spirit" rather than in "the letter" as it were.
If they paid tax it is definitely on topic IMO.
"Coporation Tax explained. If you're a limited company or an unincorporated body, such as a club, society or association, then you need to pay Corporation Tax. It's important because if you fail to pay, you could be fined daily by HMRC. ... Corporation Tax is a tax on taxable profits."
HOW MUCH DO I NEED TO PAY?
To work out your taxable profits, you start with your company's pre-tax profit for the financial year. You then:
Add back any depreciation charges you've included in your accounts
Deduct your capital allowances (they take the place of depreciation charges)
Add any other relevant income or chargeable gains
Deduct any other relevant deductions, reliefs, allowances or losses
Next:
"Apply the relevant tax rate(s) to calculate your gross Corporation Tax payable
Deduct any relevant tax credits and any Income Tax already deducted from interest income your company received (for example the tax deducted by your bank before it paid you interest)
Finally you deduct any Corporation Tax you've already paid, for example tax paid early, to find the amount of Corporation Tax you need to pay, or the amount of Corporation Tax you can claim back as an over payment."
http://www.smarta.com/advice/accounting-and-tax/tax/coporation-tax-explained/