According to international lawyer Robert Amsterdam, Spain's tax authority is pursuing what he describes as an aggressive and punitive campaign against expatriates who relocated to Spain under legitimate tax schemes.

Mr Amsterdam, who says he initially took on the matter to assist friends, claims he has since uncovered what he believes to be systemic issues within the Spanish tax administration, and that the "Spanish taxman has declared war on Brits and on other foreigners."

According to him, these issues have left many individuals facing significant financial hardship, despite their compliance with Spanish residency and tax laws.

At the centre of the controversy is Spain’s so-called “Beckham Law” — officially known as the Spanish tax regime for inbound assignees — introduced in 2004. The initiative was designed to attract foreign talent by offering beneficial tax treatment for individuals who moved to Spain for work.

Eligible individuals, such as international executives or professional athletes like David Beckham (after whom the scheme was nicknamed), could benefit from a flat 24% income tax rate and were, in some cases, not taxed on their foreign-sourced income.

Writing for the MailOnline, Mr Amsterdam says he has been "investigating a particular scam that lures foreign workers to Spain with tax breaks. Which then evaporate. A massive con trick."

He says the framework appeared straightforward and well-promoted at the time. However, he claims that many individuals who moved to Spain under this regime are now finding that their status under the law has been suddenly revoked or retroactively challenged, often without a clear explanation. Some have reportedly been hit with large tax reassessments, interest charges, and penalties dating back several years.

He alleges that this practice has left some expatriates financially devastated. “It is a massive bait-and-switch,” he argues, claiming that initial promises of tax relief were later withdrawn without due process. He says dozens of individuals have contacted him after receiving tax audit notices, sometimes years after they had moved to Spain and under the impression that their tax arrangements were in order.

In more extreme claims, Mr Amsterdam describes alleged audit tactics as intrusive and overly aggressive. He says his clients have reported auditors contacting employers, family members, schools, and other third parties, in ways he characterises as "harassing." In one case, he alleges that the stress of an audit contributed to a client's medical emergency.

He further alleges that tax inspectors are incentivised through a performance-based bonus system tied to audit outcomes, which he believes may influence their decisions to retroactively deny tax benefits. He asserts that some individuals who were previously issued formal certificates confirming their eligibility for the Beckham Law have later been told they never qualified.

When penalties and interest are factored in, Mr Amsterdam says some of his clients have been left owing hundreds of thousands of euros. He says that appeals processes are slow, sometimes taking years, during which time individuals may have their bank accounts frozen or assets seized.

He also claimed that some advisers and local professionals are reluctant to fight the system, instead encouraging settlement under threat of further legal consequences, including potential criminal charges.

The situation, he says, represents a significant legal and ethical concern, calling it a "scandal" that has affected the financial and emotional well-being of many expatriates. He says he is pursuing all available legal avenues, including action in Spanish and European courts, to challenge what he believes is a pattern of unfair treatment and to seek redress for those affected.

It’s important to note that these claims represent the opinion and analysis of Mr Amsterdam. The Spanish tax authority has not publicly confirmed or addressed the specific allegations raised. Individuals affected by Spanish tax matters should seek independent legal and tax advice.