When you sold the property, you made a gain of £56,000 (£182,000 - £90,000 - £2,000 - £4,000 - £5,000 - £25,000). The tax office may disallow some or all of any improvement expenditure that you cannot prove if they ask to see receipts and invoices. You owned the property for 276 months, of which you lived in it for 34, it was effectively vacant for 137 and it was let for 105.
The gain for the period the property was your main home is exempt from CGT as is the gain for the last 36 months of ownership. That accounts for £14,203 (£56,000 / 276 x 70). The remaining taxable gain of £41,797 is split between that part of the letting period gain which is not covered by the last 36 months of ownership, £14,000 (£56,000 / 276 x 69) and the period the property was vacant, £27,797 (£56,000 / 276 x 137).
As the property was both your main home and it was 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 £14,203 and
3 the letting period gain of £14,000.
Letting relief of £14,000 will reduce the remaining taxable gain from £41,797 to £27,797. The annual CGT exemption of £10,900 will reduce that to £16,897 on which you will pay CGT.
If all the £25,000 improvements costs were disallowed, the main residence/36 months tax free gain would be £20,543, the letting period gain would be £20,250 and the vacant period gain would be £40,207. Letting relief of £20,250 would reduce the taxable gain from £60,457 to £40,207. The first £10,900 of that would be exempt which would leave you with a net taxable gain of £29,307.
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 2013/14 tax year, one of the following scenarios will apply:
If your income in 2013/14 including the taxable gain is £41,450 or less then all the taxable gain will be taxed at 18%.
If your income in 2013/14 excluding the taxable gain is more than £41,450 then all the taxable gain will be taxed at 28%.
If your income in 2013/14 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%.
I hope this helps but let me know if you have any further questions.