Dutch banks have been sharpening up regulations for trust offices and their customers ever since the publication in April 2016 of the Panama Papers – millions of leaked documents about offshore entities.

Details of the changes were found in internal documents of Holland Quaestor, the sector lobby group, obtained by the Financieele Dagblad the paper said on Monday.

The documents show banks have become more critical about payments made through their own bank accounts, the FD said. Holland Quaestor noted in March that banks are opening far fewer accounts for letterbox companies. Moreover, charges for these accounts have risen sharply.

The tougher treatment was an initiative of the banks themselves and the Dutch central bank DNB which holds a supervisory role over the trust sector, the paper points out.

Trust offices have been under fire for many years and are often used to avoid tax and bring companies other benefits. Through them there is a risk of money laundering and involvement in terrorism, the FD said.