At the moment, the European Commission is considering the possibility to oblige the British to receive an electronic visa before they enter the European Union and pay £6 for it. After Brexit, the British will be forced to pay for the visa whenever they want to visit one of the 27 countries of the European Union. In Brussel they said: "According to the negotiations on Brexit, after March 29th, 2019, other rules will be applied to the British".
Paying for the visa will be done through the electronic system of travel authorisation (ETIAS - EU travel information and authorisation sуstem). The system, introduced for strengthening of security measures after terrorist attacks in France and Belgium, will oblige citizens of all countries with which the European Union has a visa-free regime agreement, notify about the trip and pay for it. This decision is designed “to protect the external borders of the European Union" in order to allow the European Parliament "to stop those who may threaten our citizens".