A brief summary of the impact of tax-free compensation
Expenses based on receipts are included in the total compensation. They are processed as tax-free reimbursements. When travel allowances and expenses are added to your total compensation, you won't see an increase in the overall amount; instead, the taxable portion will be reduced. If your expenses happen to be higher than your commission, they won't be included in the final calculation. Instead you can put those on your own taxation.
You can then include reimbursements based on receipts in your own taxation as income-related expenses. Example: If the commission to you is 200 euros and a partial daily allowance of 24 euros and expenses of 5.70€ are deducted, the withholding tax is only withheld from the 170.30 euro part for the Tax Administration.
A good rule is that expenses can be approximately 50% of the compensation.