Uploading of invoices can be done in either Administrator or Location Mode. Just ensure that the correct Location is selected.
On Laptop/Desktop:
Select Upload Invoice
Drag relevant files to the space within the dotted lines or click Browse from Computer
On Mobile/Tablet:
Click on the ≡ icon at the top left corner of the page to expand the menu
Select Upload Invoice
Select either Take photo of invoice or Browse from gallery
It is recommended to take photos of the invoices beforehand and select Browse from gallery to do a mass upload of invoices.