LONDON (BLOOMBERG) - The trade agreement between the United Kingdom and the European Union brought welcome relief to businesses, averting the prospect of punitive tariffs and a chaotic no-deal split from Britain's largest trading partner this week.

However, the deal leaves major issues either unresolved or at risk of flaring up again.

Here's where the Brexit accord may cause problems in future:

Level Playing Field

A deal over the so-called level playing field, creating the conditions for fair competition between businesses, was one of the thorniest parts of negotiations. The agreed compromise means the UK doesn't have to align with EU laws, but the bloc can impose proportionate tariffs, subject to arbitration, if it can show Britain's actions have distorted fair competition.

This means the question of levies on UK-EU trade is still far from settled and is a live issue. One of the central arguments of the campaign to leave the bloc was that Britain would "take back control" of its own laws, and euroskeptic members of the Conservative Party have called on the prime minister, Mr Boris Johnson, to seize the opportunity to slash regulations.

The deal also contains a "review" clause which allows either side to periodically re-negotiate this part of the treaty if they are unhappy with how it is being used. The trade deal could therefore still collapse in future if the UK or EU decide it isn't working out.

Finance

The deal offers little clarity for financial firms. There is no decision on so-called equivalence, which would allow firms to sell their services into the EU's single market from the City of London. The agreement only features standard provisions on financial services, meaning it doesn't include commitments on market access.

Mr Johnson told the Sunday Telegraph the deal "perhaps does not go as far as we would like" on financial services, in a rare admission his strategy in the talks had fallen short.

The Treasury is due to negotiate a memorandum of understanding with the EU as an urgent priority in 2021 and London will continue discussions with Brussels over access and equivalence for financial services, Chancellor of the Exchequer Rishi Sunak said on Sunday.

Data

The UK and EU have only agreed a temporary solution to keep data flowing between their territories. For an interim period of a maximum of six months, data can continue to be transferred until a separate legal agreement is reached.

EU officials have said a so-called data adequacy decision, which would certify that UK data protection standards are comparable with the bloc's, could be made in early 2021.

Fish

The Brexit trade deal contains a five-and-a-half year transition period for fisheries, during which British fleets will see an uplift equal to 25 per cent of the catch previously caught by EU boats in UK waters. After that, access will be subject to annual negotiations.

The agreement gives both the UK and EU the right to levy duties on each other's fish if they can show that any future reduction in access to waters causes economic or social harm.

There was an angry response from fisherman to the compromise, with the National Federation of Fishermen's Organisations describing it as a "betrayal." Fishing was a totemic issue in the Brexit campaign and they will pressure the UK government to drive a hard line when the next talks come around.

Gibraltar

The UK and EU are still yet to come to an agreement over Gibraltar, the British territory connected to mainland Spain. Without a deal, crossing the frontier could be more difficult, which could cause long queues for commuters and significant economic disruption. About 15,000 workers cross the border every day.

Any attempt by Spain to erode or even end British control of the territory has long raised the hackles of Conservative lawmakers, including former leader Iain Duncan Smith, and they will fight hard to stop the UK giving any concessions.