So when is payment date? I have been traveling for the last year...

So when is payment date? I have been traveling for the last year and have made no income bar interest and dividends.. If it is moved to next year when i have been working i will get smashed.. if i say have made 40k on this deal and then only need to pay cgt on 50% for having held a year does that mean i only pay tax on 2K because of the no tax on the first 18k earned a year... also can i sell shares im down on to minimise my tax requirements?