The taxman is sending warning letters to those who have now run up late-filing penalties of £1,300 for that year, under self-assessment.
They can still pay, or ask for the penalty to be taken off their income in 2013-14 if they are in the PAYE system, the BBC reports.
The letters are part of a continuing campaign against a persistent minority of non-filers.
A spokesman for HM Revenue & Customs (HMRC) said the defaulters could still pay their fines, and submit the late tax returns
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