For Charities - add a 0 followed by your 7 digit charity number.
Please provide your Sole Trader ERN or UTR number if you are a Sole Trader / private individual employing or hiring.
ERN format is: 123/XX12345, or 123/X12345 and UTR 10 digit eg: 12345 12345.
These are the ID numbers given to you by the HMRC.