In addition to travel expenses, accommodation and meal allowances, you can also deduct other costs incurred in connection with your off-site work. These include, among others:
For many incidental travel expenses, there are no receipts. You can still claim these in your tax return. Create a self-issued receipt with the location, date, type and amount of the expense and submit it.
If you do not know the exact amount of an item, estimate it. Many tax offices accept an estimated amount if it is plausible.