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
Pro Tip: It is recommended to take photos of the invoices beforehand and select Browse from gallery to do a mass upload of invoices.