I believe it has something to do with 3rd parties. I have searched for a particular flight using skyscanner and then they have sent me to Wizzair site. I saw before the end of the booking this Surcharge.

I have opened a new browser in Icognito and I have searched for the same flight directly on Wizzair (no more 3rd parties this time). Afterwards, the surcharge did not apply again anymore.

Hope this helps, Regards

I believe it has something to do with 3rd parties. I have searched for a particular flight using Skyscanner and then they have sent me to the Wizzair site. I saw this surcharge before the end of the booking.

I opened a new browser in incognito mode and I searched for the same flight directly on Wizzair (no more 3rd parties this time). Afterwards, the surcharge did not apply again anymore.