What is meant by "deterioration"?

Once you have lodged an objection, your tax office must make a decision. This means the tax officer will review your tax return point by point. As a result, they may find errors elsewhere or disallow expenses.

For example: You have objected to your tax assessment because the tax office did not recognise work-related expenses of 250 Euro. You then receive a letter from your tax office stating that the claimed work-related expenses will be recognised. However, upon closer examination, it was found that the tax office does not recognise the conditions for other income-related expenses. The removal of these other expenses may lead to an increase in your tax liability. This is permissible.

If such an increase in the tax assessment is imminent, the tax office must inform the taxpayer in advance. The person lodging the objection can generally avoid the increase by withdrawing their objection (§ 362 AO). Although your objection will then lapse and the tax assessment will become legally binding immediately, the announced increase will also be dropped.