In My Hours, users can add expenses to every time log. It is also possible to attach invoices or other files to support the entered expense. Allowed file extensions are: .pdf, .csv, .xls, .xlsx, .doc, .docx, .txt, .jpg, .jpeg, .png, .gif.
Additionally, you can create a Tag (for example: 'Expenses') and mark all such logs with it. You will then be able to filter your Detailed report by this tag to quickly find such logs.
If you need to enter only expenses without tracked time, such as an airplane ticket, you should create a time log of 0:00 duration and enter just the amount of expenses.
*** If you can't see the 'Expenses' field in the Track view, the administrator can make it visible in Account settings > Time log fields.