With increasing numbers campaigning for Britain to leave the EU, ever closer union is looking ever more uncertain.

Opinion about the positive and negative aspects of Britain remaining within the EU is diverse. Whatever decision is made, companies need to be prepared for the potential outcomes. This article looks at the likely impact of the referendum (whatever its outcome) and provides some positive steps for companies to take.

What might happen?

Since its creation, no Member State has ever left the European Union. What happens if Britain votes to leave is therefore without clear precedent.

The Treaty on European Union, like any contract, has termination and notice provisions. In simple terms, Article 50 provides Member States with the right to serve an irrevocable notice to leave.

During this two year notice period, the parties are expected to work towards a negotiated withdrawal agreement. Unless the parties reach an earlier agreement, any Brexit will take effect two years after the service of notice.

It is possible, by consent, for the parties to extend the notice period beyond two years. If Britain does vote to leave, it is likely to wish to do so as quickly as possible to minimise uncertainty within the business sector including, in particular, the financial markets.

However, any withdrawal agreement will require qualified majority voting of the remaining Member States and any further trade agreements with the EU would need to be ratified by each Member State.

Given the competing interests and concerns within the EU at present it is not hard to imagine an extended debate spanning years rather than months. Indeed, by some estimates the renegotiation of the relationship could take decades.

The prospect of such a period of uncertainty is of great concern to businesses within Britain and within the EU generally.

British companies in particular need to start considering what steps to take now to minimise any future disruption and allay the concerns of trading partners. Below, we list some of the key issues to be aware of:

EU employees

If no or no favourable agreement is reached on any Brexit, British citizens working elsewhere in the Union may automatically become illegal immigrants - as could the estimated 2.34 million EU nationals currently working in Britain.

Undoubtedly, all parties will seek to avoid such a scenario - but for companies with a substantial EU-wide presence, it is worth considering strategies for reassuring current and prospective employees on their status and potential options in the event of a positive vote to exit.

On an individual level, those who have worked in Britain (or elsewhere) long enough to apply for citizenship may wish to consider such a step prior to the referendum.

Financial services

The UK is the largest financial services centre within the EU. Not only are many global banks and financial services providers headquartered in London but many EU firms also maintain branch presences here.

One of the key benefits for financial services in London is the EU "passport" system. This is a system permitting financial services operators legally established in one Member State to establish or provide their services elsewhere within the EU without the need for further authorisation.

If you are a financial services institution currently relying on the passport system, issues to consider include the extent to which branches and subsidiaries may still benefit from EU policies post-Brexit. In particular, it will be necessary to consider the extent to which subsidiaries in other Member States may need to be established to ensure continued reliance on the 'passport' system.

Contracts

Over the next few months, companies need to look closely at the likely impact of any Brexit on key contracts. Many commercial contracts may refer to European legislation or refer to EU legal concepts- in particular in the fields of data protection, employment, environmental law.

Additionally, parties may wish to reference any potential Brexit as an event which necessitates a revision or renegotiation of key terms.

Companies also need to consider the impact of English law and jurisdiction clauses. For the most part, it is hard to see whether there will be a clear reason to depart from such clauses in anticipation of a Brexit but it is important to bear in mind that without some form of reciprocal agreement being reached, the current benefits in relation to choice of law and jurisdiction and - crucially - enforcement of judgments within the EU, will be lost.

Practical steps

Much has been made in the press of campaigns of 'fear' and inflated claims regarding the pros and cons of any Brexit. What is clear, however, is that the genuine possibility of a British vote to exit from the EU in three months' time means that businesses need to start thinking now about how to protect their workforce, their commercial interests and their trading relationships.