HM Revenue & Customs (HMRC) is preparing a major new enforcement push targeting undeclared income from online sales, armed with fresh data on nearly four million sellers that reveals a staggering £55 billion in total earnings for 2025.
According to figures obtained through a freedom of information request by accounting firm BDO, HMRC received reports detailing the incomes of 3,988,892 online sellers in calendar year 2025 – a dramatic 272% increase from the 1,466,171 reports received for 2024, when earnings totalled £25.5 billion.
The data, shared under new international reporting rules, comes from a wide range of digital platforms. These include online marketplaces like eBay and Vinted, short-term accommodation sites such as Airbnb, food delivery and private hire apps, and content-sharing or service platforms.
Platforms are required to report details on sellers who exceed certain thresholds, typically more than 30 sales per year or earnings above roughly £1,700, regardless of whether the activity generates a profit or is classified as casual selling versus trading.
HMRC is in the final stages of building an automated system to extract and analyse this influx of information, which it will use to identify potential under-reporting or non-compliance.
The authority has already sent “nudge” letters to suspected non-reporters in previous years, and further compliance checks, investigations, and enforcement actions are expected later in 2026.
Dawn Register, a tax dispute resolution partner at BDO, described the development as a “game-changer” for HMRC.
“HMRC have been concerned for some time that large numbers of people may have been under declaring incomes earned via digital platforms – but up until now, they haven’t always had the information to prove it,” she said.
“This new data will be an absolute game-changer for HMRC – and a goldmine for tax inspectors seeking to ensure that online sellers pay the right amount of tax. With a staggering £55 billion of online sales reported to HMRC for 2025, the tax authority will have a huge new target to aim at.”
Experts are urging affected individuals, such as side-hustlers, casual sellers, and those running small online businesses, to review their tax positions immediately.
Many may need to register for Self Assessment if they haven’t already, especially if their trading or miscellaneous income exceeds the £1,000 annual trading allowance.
The tax authority has provided an online tool to help individuals check if they need to report income from online platforms.
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