The Belgian Special Tax Inspectorate (STI) is looking for Belgian individuals who have invested in cryptocurrencies in foreign exchanges, local news outlet De Standaard reported Friday, March 2.

After receiving information from Finnish authorities that several Belgian taxpayers had been trading on Finnish crypto exchanges, the STI started looking into the cases of three Belgians involved, with a fourth file closed as a “non case,” The Brussels Times wrote.

According to a rule introduced in Belgium last year, crypto speculators are obliged to pay a 33 percent tax on crypto profits, filed under the “various income” section on the tax form.

Due to the anonymous nature of crypto trading platforms, De Standaard writes that the crypto tax rule has been hard to enforce. However, the STI plans to follow the example of the US’s Internal Revenue Service (IRS), which legally compelled US-based crypto exchange and wallet Coinbase to turn over the data on around 13,000 customers for tax enforcement purposes.

Belgian tax authorities will try to use the double taxation treaty between Belgium and the US as a way to get information about possible Belgian Coinbase users, according to De Standaard. The STI also plan to send similar requests for information to crypto exchanges generally to find out whether any Belgian taxpayers are customers.

Francis Adyns, a representative from the FPS Finance, a Federal Public Service of Belgium, told De Standaard:

“It will be investigated whether a similar question can be asked as that of the IRS […] There are several other websites that deal in bitcoins and many other crypto coins. Every known website in this domain can count on our explicit attention.”

While the IRS had initially asked Coinbase to turn over information on all of its users, a court case brought on by Coinbase decided in Nov. 2017 that only information on “high volume” users needed to be given to the IRS.