The services falls under Electronic Services and POS is based on place of use and enjoyment. In the absence detailed guideline for UAE VAT, one can refer KSA guidance for assessing the place of use/enjoyment. As per KSA guidance use and enjoyment can be assessed based on the place of residence of the recipient of service (Eg: billing address, payment bank etc). If there is sufficient evidence to support that the participant is a resident of UAE, would suggest to charge VAT. Would also recommend to collect basic details from the participants of your webinars to determine the residence. If the participant is a non-resident then VAT need not be charged.