In the profit and loss section we can see the line item “Development management losses”. By searching the ESEF taxonomy we know there isn’t a prescribed tag matching this. With this in mind, we need to create an extension. To do this we copy and paste the name of the line item to create the new tag name and apply the basic properties of instant /duration, in this case duration as it is a profit and loss item, and as a debit as it is an expense item. The next step is to anchor it to the relevant wider tag of, ” Operating Expense”. By doing this, we have successfully created the extension and this extension can now be used as a normal tag.