Prior to the 5th April 2016, directors could take up to the basic rate tax threshold (currently £45k) in salary and dividends without incurring any personal tax.
Now, there will be a tax of 7.5% on any dividends over £5k, during any personal tax year (6th - 5th April).
The new dividend tax kicked in on the 6th April 2016, so will form part of your personal tax return for the period from 6th April 16 to 5th April 17. This tax will need to be paid by 31st Jan 18.
To help you budget for this, we'll update everyone's bookkeeping spreadsheet by the end of April 2016 so that it includes an estimate of this additional personal tax.