You should refer to HS283 here
for information on the main home and CGT.
None of the maintenance costs can be claimed against the sale proceeds unfortunately. They should have been claimed against the rental income. Again, unfortunately, you cannot claim any relief for having to move into your father's home to look after him.
If you sell the property for £230,000 in August 2015 having paid £49,000 to buy it and having paid £23,000 to extend the lease, you will make a gain of £158,000. You can deduct the costs of buying and selling the property (legal fees, stamp duty, survey fees, selling agent fees etc) which will reduce the gain further. By August 2015, you will have owned the property for 229 months of which you will have lived in it for 80 and let it for 149.
The gain for the period the property was your main home will be exempt from CGT as will the gain for the last 18 months of ownership. That accounts for £67,616 (£158,000 / 229 months x 98 months). The remaining non-exempt gain is £90,384 and this covers that part of the letting period not covered by the last 18 months of ownership (£158,000 / 229 x 131).
As the property has been both your main home and let, you will be entitled to a further deduction called letting relief which will be the lesser of:
2 the gain for the period that the property was your main home, £67,616 and
3 the gain for the letting period, £90,384.
Letting relief of £40,000 will reduce the remaining non-exempt gain of £90,384 to £50,384 and the annual CGT exemption of £11,100 will reduce if further to leave you with a net taxable gain of £39,284.
There are two rates of CGT, 18% and 28%. The rate or combination of rates that you will pay will be dependent on the level of your income in the tax year that the property is disposed of. If the sale occurs in 2015/16, one of the following scenarios will apply:
1 If the sum of your income and the net taxable gain is £42,385 or less in 2015/16, then all the taxable gain will be charged to CGT at 18%.
2 If your income alone is £42,385 or more in 2015/16, then all the taxable gain will be charged to CGT at 28%.
3 If your income alone is less than £42,385 in 2015/16 but greater than £42,385 when the net taxable gain is added, then part of the net taxable gain will be charged to CGT at 18% and part at 28%.
I hope this helps but let me know if you have any further questions.