A If you gift the property in May 2014, by that time you will have owned it for 83 months of which I'm assuming you will have lived it for 16 months (July 2007 to October 2008) and it will have been let from November 2008 to May 2014, 67 months. The gain will be £220,000 (£700,000 - £480,000).
The gain for the period the property was your main home will be exempt from CGT as will the gain for the last 36 months of ownership. That will account for £137,831 (£220,000 / 83 x 52). The remaining taxable gain of £82,169 will be that part of the letting period gain which won't be covered by the last 36 months of ownership (£220,000 / 83 x 31).
As the property will have been both your main home and let you are entitled to letting relief which is the lesser of:
2 the sum of the main residence gain and the gain for the last 36 months of ownership of the property which is £137,831 and
3 the letting period gain of £82,169.
Letting relief of £40,000 will reduce the remaining taxable gain to £42,169 and the annual CGT exemption of £10,900 will leave you with a net taxable gain of £32,169.
There are two rates of CGT, 18% and 28%. The rate or combination of rates you will pay will be dependent on the level of your income in the tax year of disposal of the property. Assuming you gift the property in the 2014/15 tax year and the tax rates and bands are the same as for 2013/14, one of the following scenarios will apply:
1 If your income in 2014/15 including the taxable gain is £41,450 or less then all the taxable gain will be taxed at 18%.
2 If your income in 2014/15 excluding the taxable gain is more than £41,450 then all the taxable gain will be taxed at 28%.
3 If your income in 2014/15 excluding the taxable gain is less than £41,450 but more than £41,450 when you include the taxable gain then part of it will be taxed at 18% and part at 28%.
B As a non-domiciled individual, only your UK based estate will be liable to IHT when you die unless you assume a UK domicile. See here for more on that. If you live for at least seven years after making the gift, you will have reduced your estate by the value of the gift successfully and no IHT will be payable on it by you, your brother or your estate.
If you die before the seven years is up, the value of the gift will be included in your estate for IHT purposes. Assuming your UK estate will be worth more than £325,000 (the current nil-rate band), your estate will pay IHT at 40% on the excess over £325,000. Your brother would only need to contribute to the IHT liability if your estate did not have enough assets and cash to pay all the IHT due. See here for more information on who pays IHT. So, on a property worth £700,000, the potential IHT is £280,000 but the longer you live after making the gift, the greater the potential for a discounted IHT liability on gifts made in the seven years before you die. See here under "Applying ‘Taper Relief’ to gifts" for more on that.
Your brother's estate would have IHT to pay when he dies on his UK assets assuming he doesn't assume a UK domicile and their value exceeds the nil-rate IHT band in force at the time.
There is only Stamp Duty to pay if cash is involved in a property transfer. A mortgage is cash for Stamp Duty purposes as you will read here. If you pay off the mortgage before you give the property away, there will be no Stamp Duty to pay. You may have problems with your lender if you want to give the property away as they have a charge over it.