Dividends and personal allowances
Although from 6 April 2016 the first £5,000 of dividend income is taxed at 0% it can affect the rate of tax payable on other income as it is still taxable income.
So if you have employment income of £100,000 and dividend income of £5,000 your taxable income will be £105,000 so you will lose £2,500 of your personal allowance increasing your tax bill by £1,000.