UK taxpayers have until midnight Oct. 31 to file paper tax returns. Crediut: Peter Dazeley/Getty Image. Key Takeaways Crypto profits are subject to capital gains tax in the U.K. Investors wishing to file a paper tax return for 2024-2025 must do so before the end of October. Online submissions will still be possible after the Halloween cutoff. With HM Revenue & Customs (HMRC) ‘s key deadline approaching, U.K. taxpayers have until the end of October to file paper tax returns for the year ending Apr ...