Twenty-two people have been detained as part of a major investigation into a suspected VAT fraud worth hundreds of millions of pounds.
Many of the arrests were made by police in Scotland
Customs officers, supported by police, detained the 22 in London, Manchester and Glasgow early on Tuesday.
The operation is the biggest ever undertaken by HM Revenue & Customs and used more than 60 search warrants.
It is targeting "carousel" fraud, in which goods are repeatedly exported and imported and unpaid VAT pocketed.
About 400 HMRC criminal investigators are being supported by 100 police officers from Strathclyde, Greater Manchester and the Metropolitan Police in the inquiry.
Fifteen of the detentions were in the Glasgow area, five in the Manchester area and two in London.
Gordon Miller, deputy director of HMRC Investigation, said the operation was part of a "large-scale, international criminal investigation into frauds that may run to hundreds of millions of pounds".
"Organised criminals are attacking the tax system, with the aim of stealing huge amounts of revenue," he said.
"The scale of the problem across Europe is unprecedented, and HMRC has significantly strengthened its response to this serious fraud."
The investigation is focused on a highly sophisticated scam known as carousel fraud.
It involves importing small, high-value goods, such as mobile phones, free of VAT from EU countries, then selling them with 17.5% tax added in the UK.
Instead of handing the VAT to the Government, the importing company run by criminals is shut down and the cash is kept by the importers.
This loss of tax is often compounded when the new owners of the goods export them again and can legally reclaim the VAT they paid.
Goods go round in a "carousel" via bogus supply chains within and beyond the EU because they are repeatedly imported and exported.
Carousel fraud is estimated to have cost the UK Exchequer up to £1.9bn in stolen VAT revenues between 2004 and 2005.