A pensioner from Oxfordshire said he almost had to sell his house after waiting nine months for benefits.
Fred Harriss, 82, from Charlbury, got the basic pension but should have also received pension credits, housing and council tax relief from January.
In that "miserable" time Mr Harriss struggled to care for his partner and suffered a near fatal illness.
The Department of Work and Pensions said it "sincerely apologised for the delay in processing the application".
Mr Harriss, who worked as a blacksmith until his retirement at 81, was receiving a £97-a-week pension but had to spend a quarter of that on council tax.
Jessica Brown, from Age UK, helped him to make the application for his benefit payments.
She said: "I believe if Fred hadn't had extra help then he would have given up.
"It was having a real impact on his health."
She said that the Department of Work and Pensions needed to improve its systems.
"It needs one person to take ownership of a claim and to make sure things happen.
"They are taking steps to look at the situation and remedy it," she said.
Mr Harriss is now expecting to receive £86 in compensation for his inconvenience.