WARSAW, Nov 23 (Reuters) - Polish regulator UOKiK has started proceedings against PayPal over possible prohibited contractual provisions, it said on Wednesday, adding that the possible fine could amount to 10% of the company's revenue.

It added it has doubts regarding the payments company's right to impose contractual penalties, such as blocking access to accounts, financial sanctions, or terminating contracts among others. (Reporting by Alan Charlish and Anna Koper; Editing by Louise Heavens)