To enable split expenses claims within Natural HR go to:

Administration -> Company -> Settings -> Expenses -> Expense Settings

Within Expense Settings under the Features section find the option labelled 'Allow expense and mileage claims to be split'

By settings this option to 'Yes', expense approvers are given the option to split an expense or mileage claim in order to approve part of it and decline the rest if it does not meet requirements. When the approver goes to approve an expense/mileage claim they will see a checkbox next to each line which allows them to choose which lines to split into a new report:

Once the approver has check the lines they wish to split they can click the black 'Split' button at the bottom of the page. The lines which have been selected will then be transferred into a new expense report for the approver to action. A blue banner message will be displayed at the top of the screen containing a link to the new expense report: