This deduction is applied to lower the tax base and thus reduce the tax payable. The "50% deductible" scheme may apply to various types of expenses, depending on the tax legislation and specific rules in your country. It may relate to costs such as professional expenses, business expenses, specific investments, or other allowable deductions.

For example, if you have spent €1,000 on deductible expenses and these costs are considered "50% deductible," you can deduct €500 from your taxable income. This means that you ultimately pay tax on a lower amount, resulting in a reduction of the tax owed.

It is important to note that the deductibility of costs may vary depending on the specific rules and limitations of the tax legislation in your country. It is recommended to contact a tax advisor or the tax authorities for detailed information on the specific deductibility rules and their applicability to your situation.