First, you need to create either a rental, utility, or a combined invoice and not send them out to the tenants. Once the invoices are created find them under ‘Invoices’ - ‘Sales invoices’ - ‘Unsent invoices’. Then tick the invoice you wish to share the cost between and click on ‘Choose bulk action’. From the drop-down menu select ‘Add extra rows to select invoices’. 

This opens a pop-up window with the extra invoice row. Now all you need to do is fill out the information accordingly. Choose how to divide the cost (by unit area or equally among units. Enter the sum which needs to be divided, the system calculates it accordingly for each invoice. Add the right article, write the description of the cost, choose the unit for the cost, VAT will be filled out automatically based on the article, and choose the rental object the cost applies to. You can add as many rows as you wish. After you’re done click ‘Add rows to invoices’. 

You can click on any of the invoices and see that the extra row has been added to it with the cost sum divided and added to the initial sales invoice’s sum.