HMRC requires you to clearly identify what each tagged number is in your document. To accomplish this, XBRL uses the concept and additional fact properties, such as unit type and accuracy. Most concepts for numeric facts have unit types that clearly identify what the number is. For those that don’t, you need to apply a unit type and accuracy.
NOTE: Unit types are created for you and available in the Fact Properties panel below the document.
To better understand units, consider the following:
All XBRL for HMRC concepts have a unit type, such as monetary, percent, string, or boolean.
Each numeric concept also has a unit type.
Each concept type determines which units you can use for that fact. For example, a monetary concept type allows you to use only currency units, such as a net profit concept using GBP as the unit.
Most numeric fact concepts already have the correct unit type associated with them. For example, concepts for number of shares have the unit type of shares.
Sometimes you may have a monetary concept type that needs the correct unit to specify what the number is.
For example, share-based concepts are monetary. So you need to specify which currency unit applies to the concept, such as GBP per share.
NOTE: Contact your CSM if you need a unit type created.
Commonly Used Units
When deciding on a unit, you must take into account the item type of the concept, and then use an appropriate unit.
The standard, predefined units available for HMRC XBRL include the following:
Common currencies, such as GBP
£ per share
Number, such as percentages, rates, and ratios
NOTE: Units are predetermined based on the Unit Type Registry (http://www.xbrl.org/utr/utr.xml).
Applying Units and Setting Accuracy
With your document open in Wdesk, select the fact. Click the Fact Properties icon (the X) in the lower right corner of the editor window.
NOTE: A fact might still appear red if XBRL doesn’t recognize what the number is.
Select the appropriate Unit and Accuracy.
After selecting the Unit and Accuracy, click the green Apply Property Changes checkmark to save your changes. Then Share the changes.
Viewing Additional Unit Information
You can click the blue Information icon to see more information about the unit. Additional information includes the Unit ID, Unit Type, Unit Measure, and Unit Description.
NOTE: Editing is available only for custom units. Contact your CSM for more information about custom units.