You can also validate the format of certain fields in your data by creating a custom expression in the Expression Editor. To open the dialog, right-click on the column header and from the drop down menu, select Insert Column > Custom. The Expression Editor dialog will open, with the title New Transformed Column with Custom Rule.
You can validate if a field value is in a valid National Insurance number format by using the Check If… National Insurance Number (UK) or Check If Not… National Insurance Number (UK) functions.
