The costs of the stocks for CGT purposes is what they were worth when your wife passed away. If you now sell them at a profit compared to the probate value, the first £11,100 of gains you make in the current tax year will be tax free and you will pay CGT at 18% or 28% or a combination of the two rates depending on the level of your income. You would need to work out what the CGT cost of £50,000 of the shares you might sell is as a proportion of the whole portfolio to determine the gain.
I hope this helps but let me know if you have any further questions.
If you were a basic rate taxpayer in 2015/16 (gross income no more than £42,385), you will have no tax to pay on dividends received in that tax year.
In 2016/17, the first £5,000 of your dividends will be taxed at 0%. To the extent that the balance of your dividends are in the basic rate band in 2016/17, they will be taxed at 7.5%. Any dividends which take your gross income over £43,000 in 2016/17 will be taxed at 32.5%.
You can make £11,100 of gains in 2016/17 tax free. If the share portfolio you inherited has increased in value since January by £5,000 you can sell it all and pay no CGT. CGT is charged at 10% on basic rate taxpayers in 2016/17 and at 20% on higher rate taxpayers in 2016/17.
If you sell the whole portfolio in 2016/17, you will need to complete a tax return after the end of the tax year even if the gains are within the CGT exemption and you have no CGT to pay.
You are currently sitting on gains of £5,000 on the shares you inherited. I'm not aware of any other shares you may have. You can make £11,100 of tax free gains in 2016/17 which is more than £5,000. The CGT exemption will be at least £11,100 in the 2017/18 tax year so I'm not sure how you came to the conclusion that you would be taxed in the next tax year. Nobody knows where share prices will be in a year's time so if you kept the portfolio, it might be worth more or less than it is now.
All your assumptions are correct. There is no time limit by which you need to liquidate your late wife's shares.
You can sell your wife's shares for whatever they were worth at probate plus £11,000 (the annual CGT exemption) provided you don't makes gains on any shares or property you own yourself in the same tax year.
You already have.