Here's how to add an expense:

1. Go to Expenses and click "Add"
2. Enter the supplier, category, description, amount, and date. An amount is required; the form will not save an expense of EUR 0.00 unless it is a genuine zero-value record such as a VAT-only credit note.
3. Save the expense so the record is created
4. If you want to attach a receipt, open the saved expense and use "Upload Receipt" on the detail page

Tip: Receipt upload happens after the expense is saved, not on the new-expense form itself.