Hi again.YOUR HUSBAND
If he gifted his 50% share, he would have a gain of £117,000 (£300,000 - £66,000 / 2). The gain for the period from February 2004 to October 2015 (say), 141 months, would be tax free. That would amount to £76,375 (£117,000 / 216 months x 141 months). That leaves £40,625. The first £11,100 of that would be tax free to leave a net taxable gain of £29,525.
There are two rates of Capital Gains Tax in the UK, 18% and 28%. The rate or combination of rates that he will pay will be dependent on the level of his income in the tax year the gain occurs. Take a look here
for information on how to calculate your CGT rate. The CGT liability would be somewhere between £5,314.50 (18%) and £8,267.00 (28%).
Giving away one-sixth of his share would leave a gain £19,500 of which £12,729 (£19,500 / 216 x 141) would be covered by main residence exemption and the balance of £6,771 would be covered by the annual CGT exemption.YOU
You would have a gain of £117,000. The first £11,100 would be tax free leaving you with a net taxable gain of £105,900. The maximum CGT liability would be £29,652 (28%). If your income is not £42,385 or more, than part of the net taxable gain will be charged to CGT at 18%. That could be as much as £31,785 if you had no income whatsoever.
Giving away one-sixth of your share would leave you with a gain £19,500 with the first £11,100 being covered by the annual CGT exemption. The balance of £8,400 would be liable to CGT.