Prudential has been told to cough up compensation for administrative errors that spanned more than two decades.
On March 12 1990, a complainant referred to as Mr K left his occupational pension scheme.
Prudential claimed it received no instruction from the employer to remove Mr K's policy from the plan, which was subject to an annual flat rate charge.
On January 31 2006, Mr K called Prudential as he was considering a transfer to another scheme so requested a transfer value.
Prudential's notes show that the call handler requested transfer discharge paperwork be sent to him.
The illustration, dated February 1, 2006, quoted a surrender value of £480 and stated that Mr K had withdrawn from the plan on March 12, 1990.
The illustration did not contain information about applicable charges.
In June 2012, Mr K called Prudential but was told that he had no authority to speak to the provider about his benefits.
However it was in May 2018 that Mr K raised a formal complaint when he was told his surrender value had reduced to £46.
Considering the complaint, Pensions Ombudsman Anthony Arter said as the illustration issued in 2006 showed Mr K’s correct leaving date, Prudential ought to have known that Mr K had left the plan.
In spite of this and Mr K's request to receive his plan information directly, Mr Arter said Prudential continued to send information to the trustees depriving him of the opportunity to mitigate his losses.
Mr Arter said Prudential compounded this issue when, in 2012, it refused to speak directly to Mr K, incorrectly claiming it had no authority to do so.
But Prudential argued as Mr K did not transfer in 2006 because the transfer value was too low for a receiving scheme to accept the provider shouldn’t have to compensate him as he couldn’t have done anything to mitigate his losses until 2017, when he turned 55.
Mr Arter said: "Given Prudential knew that Mr K had left the plan in 1990, it ought to have issued statements directly to him from this time (2006). Its omission to do so amounts to an administrative error.
"To deny Mr K information to which he was entitled, has denied him the opportunity to monitor the value of his pension benefits.
"Prudential provided correct information to Mr K for the first time in 2006, some 16 years after he left the plan.
"Prudential's claim that Mr K could not have transferred to another scheme in 2006 due to the low transfer value is unsubstantiated by evidence.
"When Mr K called in 2012, Prudential incorrectly told him it was not authorised to speak to him about his benefits, which is a further administrative error and compounded the issue of Mr K not being sent information about these benefits from 1990.
"Prudential's administrative errors have spanned a significant period of time and have caused missed opportunities for Mr K to mitigate his losses. I find that Prudential has caused Mr K serious distress and inconvenience through its errors."