Complaints against HMRC from pensioners have risen over the past year, according to the Revenue's watchdog.
Adjudicator Judy Clements says a disproportionate amount of pensioners complained about treatment by HMRC.
Clements writes: "When I took up office I became aware of the growth in volume of taxation cases and the impact HMRC's decision making was having on some customer groups, particularly pensioners.
"My initial meetings with the Parliamentary and Health Service Ombudsman (PHSO) indicated they too had serious concerns over HMRC's handling of these cases."
She says in recent years there has been growth in cases where HMRC's decision-making has had an adverse impact on vulnerable groups of people, for example pensioners facing unexpected tax bills.
The report says HMRC was ordered to pay over £100,000 in compensation to people who were judged to have been treated unfairly in the tax year 2009/2010.
Procedures to improve taxpayers' experiences, however, have been put in place. The report says the Adjudicator's Office has worked with HMRC to develop workshops for complaint handlers "emphasising the need to provide clear, evidence based explanations and reasons for their decisions".
Additionally, an "audit template" to help complaint handlers follow guidelines has now been made a mandatory part of reviewing cases.
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