The European Union will agree on its common position for negotiations with the U.K. government at a summit on April 29.
The 27 countries want, above all, to show they are united in the process that will see the U.K. leave the EU. However, countries do have specific concerns about the exit process and what it means for them.
CNBC takes a look at what the main concerns are for each of the 27 countries ahead of negotiations.
Countries concerned: Austria, Germany, Lithuania, Denmark, Finland, Slovenia, Sweden
Money, money, money. Many of the 27 members are concerned that the U.K.'s departure will mean higher contributions to the European budget.
The U.K. is currently one the bloc's biggest economies and a net contributor to the EU budget. In 2014, the U.K. was the fourth largest national contributor, after Germany, France, and Italy. It paid a total of 11.34 billion euros ($12.24 billion) to a budget of 116.53 billion euros.
Austrian Chancellor Christian Kern said in early April that the EU should seek to limit any extra costs in the next budget, the Austrian Press Agency reported. Ministers in Germany and Denmark have made similar comments.
Danish Minister of Finance, Kristian Jensen, told the economic newspaper Borsen that Denmark will not pay more into the EU budget after Brexit and the EU budget should, in fact, be cut.
As a result, the lack of U.K. contributions to the EU budget is also a concern for net receivers. For example, the Lithuanian government has said that the U.K. needs to honor the budget commitments that it has made to the several EU programs, including the dismantling of a nuclear-power plant in Lithuania, even after it left the bloc.
Countries concerned: Belgium, Hungary, Czech Republic, the Netherlands
Trade is the big elephant in the room given the strong links between British and EU-based businesses that could be damaged as the U.K. leave the EU's single market. To compensate, the U.K. wants to negotiate a free-trade deal with the EU during Brexit talks, but the EU is only willing to do it after they've established "divorce" proceedings.
In Belgium, the northern region of Flanders is responsible for 87 percent of Belgium's exports to the U.K., Politico reported, and as a result, it is pushing for an agreement with the U.K. on trade. However, Belgium's southern region of Wallonia is famous for delaying trade deals. It recently blocked the approval of a trade agreement with Canada on concerns that it would impact its agricultural industry.
The Czech Republic wants the EU and the U.K. to keep current economic ties intact, as much as possible and has spoken against imposing tariffs on British products.
Countries concerned: France, Croatia, Ireland
Britain's departure from the EU raises many questions regarding the future of current borders. The most obvious one is the border between Northern Ireland and the Republic of Ireland. Both the EU and U.K. agree that they need avoid a hard border in the region due to its history.
In Calais, the problem is similar. The French town is the first point of entry for many U.K. goods as they try to reach Europe. Furthermore, thousands of migrants and refugees occupy the area as they try to enter the U.K. by stowing away on lorries, cars, and trains.
Croatian officials are relieved that they joined the EU at the right time, but they are concerned about the future of neighboring countries. Croatian Foreign Minister Miro Kovac said Brexit would delay the entrance of new members to the bloc as the EU focuses on its inner problems first. The Balkan countries of Albania, Serbia, Kosovo, Montenegro, Macedonia and Bosnia are at different stages of their accession to the EU. If the EU sends any signs that their accession is compromised, they might turn their back on the EU.
Countries concerned: Poland, Portugal, Italy, Czech Republic, Spain, Estonia, France, Greece, Latvia, Lithuania, Cyprus, Bulgaria, Romania, Slovakia
One could nearly include all 27 countries in the list above. According to 2014 figures, the U.K. had a population of 63.7 million, of which 2.9 million are from Europe. The number isn't significant in the grand scheme of things, but it was the main argument that pro-Brexit campaigners used.
European officials made this issue their priority and wanted reciprocal guarantees for EU nationals living in the U.K. to make sure they are not affected by Brexit and British citizens living in EU countries will not be impacted either.
The issue is so important that Milan Chovanec, the Czech interior minister, said in January his country would seek an agreement on this issue even if that means doing so bilaterally. The U.K. Prime Minister Theresa May has agreed to strike an agreement on this "early" in the process.
Countries concerned: Luxembourg, the Netherlands, France, Ireland
It is uncertain what will happen to the City of London, including how much of the industry will want to move to Europe. Either way, EU capitals are hoping to host them. Xavier Bettel, the prime minister of Luxembourg, said recently that some firms had shown interest in moving operations to his country. Luxembourg is also hoping to host the European Banking Authority, which is currently in the U.K.
Countries concerned: Spain
This is perhaps the only issue in Brexit talks that only one EU country is worried about, but it has already raised anger between the U.K. and EU - even before negotiations have started. The EU has written in its draft guidelines that there cannot be any deal between the EU and the U.K. that applies to Gibraltar without the consent of Spain.
The sovereignty of Gibraltar has been a contentious issue between the U.K. and Spain for centuries. The territory is self-governed in all matters excluding foreign policy and defense, which are decided in the U.K.
Fabian Picardo, chief minister of Gibraltar, told CNBC earlier this month that Spain has behaved in a "quite abominable" way.
Countries concerned: Germany, Finland, Malta, Sweden
The main aim of European officials is to keep the 27 EU nations together throughout the Brexit process. The European Commission, which is the main negotiator on behalf of the 27, has a clear mandate: leaving the bloc needs to be worse than being part of the European Union.
Michel Barnier, the EU's lead negotiator, said earlier this month: "Unity is essential, for our Union but also for our British partners: at the end of the day if the Union is disunited, there simply will not be an agreement."