European rules designed to make it harder for wealthy individuals and companies to hide their cash offshore have loopholes that mean foreign accounts can be kept secret from tax collectors, a report has warned.

Countries in the EU have exchanged financial information about accounts held by overseas residents since the introduction of the “common reporting standard” in 2017, designed to reduce tax evasion.

Information on offshore holdings is sent to the country where the account owner is registered as resident, where authorities can then ensure the money is appropriately taxed. Information is also shared with and by low-tax jurisdictions such as the Cayman Islands.

But while the rules make it easier for countries to see what money is owed, wealthy investors and companies can use loopholes, according to the report by the European Green party, shared with the Guardian.

One problem is that not all countries are taking part in the exercise; the US is one of the key players missing. It has committed to sending partial information, but individuals can still hide their identities behind companies.

Austria and Bulgaria do not receive information from the US, the report said, and as of June 2018, at least 43 countries were not committed to implementing the common reporting standard, including Montenegro, Serbia and Ukraine. The report said the easiest way for an EU citizen or company to avoid the automatic exchange of information was to set up bank accounts in one of these countries or in the US using a company name.

Another loophole involved countries that offer so-called golden visas to wealthy investors who commit large sums of money in exchange for citizenship.

In a scenario set out in the report, someone living in Italy could buy citizenship in Cyprus, which has agreements to receive information from only 33 jurisdictions in or related to the EU. Any account the person opened in a country that fell outside that arrangement would in effect remain invisible.

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Additionally, there are no sanctions for tax havens that fail to send the relevant information to EU countries, and the rules apply only to financial holdings and not to other assets someone may own overseas. Other rules introduced to make countries tell each other about cross-border tax agreements with companies also needed changing, the report said, so that the details were made public and included all rulings involving multinationals.

Sven Giegold, a German MEP and member of the European Green party, said: “The automatic exchange of information is great progress against tax evasion. Now Europe has to close these loopholes so that the end of tax havens will not become an empty promise.”

The report called for the European commission to revise the rules so all financial centres and tax havens are forced to share information with member states, with the risk of sanctions if they do not. It also suggested that the EU could ensure that any advice or request to transfer money to the US be considered as an avoidance scheme until it shares as much information as required by the common reporting standard.