On Social Welfare and going through payeonline to check if I am due tax back in the last 4 years. How do I work out the calculation or where does it say the figure for each year?
You won't actually get a figure unless you request P21 for each year. You just need to be sure that you are claiming all your allowances (and that your incomes are declared accurately). I think P21 will be delivered online within a few days.