Any statement of withdrawal must be unqualified and unambiguous. It may, however, be conditional upon, e.g. avoidance of publication or refund of the examination fee. An unqualified and unambiguous withdrawal becomes effective the day it has been received by the EPO.
If such a statement of withdrawal is made orally during oral proceedings, then either a (handwritten) signed confirmation is to be submitted during the proceedings or the division has to confirm the withdrawal in the minutes and read out the corresponding passage for confirmation in the oral proceedings. The withdrawal has effect from the date of the oral proceedings.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/e_viii_8_3.htm
Date retrieved: 17 May 2021