The following figures are for each of you as I have divided the gain in two.
If you sell the property after 5 April 2014 without it having been your main home at some point, you will each have a capital gain of £78,250 (£400,000 - £243,500 / 2). The first £11,000 of your respective gains will be exempt so you will each be left with a net taxable gain of £67,250.
If you sell the property on 5 April 2015, having lived in it for 12 months, you should each qualify for exemption from CGT for 18 months worth of the gain. That will account for £19,295 (£78,250 / 73 months x 18 months). The remaining gain of £58,955 is that part of the letting period gain which is not covered by the last 18 months of ownership, of which you will have occupied the property for 12 (£78,250 / 73 x 55).
As the property will have been both your main home and let you will be entitled to letting relief which will be the lesser of:
2 the sum of the main residence gain and the gain for the last 18 months of ownership of the property, excluding overlaps, which will be £19,295 and
3 that part of the letting period gain not covered by the last 18 months of ownership of the property which will be £58,955.
Letting relief of £19,295 will reduce the remaining gain from £58,955 to £39,660 and the annual CGT exemption of £11,000 will reduce it further to leave you with a net taxable gain of £28,660.
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 sell the property in the 2014/15 tax year, the following will apply:
1 If your income in 2014/15 including the taxable gain is £41,865 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 £41,865 then all the taxable gain will be taxed at 28%.
3 If your income in 2014/15 excluding the taxable gain is less than £41,865 but more than £41,865 when you include the taxable gain then part of it will be taxed at 18% and part at 28%.
HMRC have recently been winning tax tribunal cases where they have challenged the taxpayer's claim for the main residence exemption as a result of a short period of occupation of the property which they say was only to reduce the taxable gain and not as a result of an intention to make the property that property their home so you need to be aware of that.
As you will have seen from my calculations, it is not simply a matter of saying a property is your main home and getting the main residence exemption. It depends entirely on the facts and figures. You are currently given the last 36 months of ownership of a property as a CGT exempt period where it has at some point been your
main home. That is being reduced to the last 18 months for disposals of property after 5 April 2014. By moving into the property for a year or so, you should be able to reduce the taxable gain by about £38,250 for each of yourself and your husband.
Take a look at the HMRC helpsheet HS283 here for more information on the main residence and CGT.
I hope this helps but let me know if you have any further questions.