A quarter of the complaints against the service were awarded, 565 of the 2,215 total complaints received between January and December last year.
The FOS said its average award for a complaint in 2015 was £193.34, according to a freedom of information request.
This is up 8% from the previous year when the average award was £179.
As a proportion of complaints, the rate of pay-outs has gone up from 23% in 2014 to 25% last year.
However, both the number of complaints and awards decreased.
Complaints dropped 15% from 2,609 in 2014 to 2,215 the year after and awards fell 7% from 610 in 2014 to 565.
Coincidently, this leaves the sum of awards compensated as the same for both years at £109,000.
The most common ‘primary concern’ of FOS users was timeliness, with 562 complaints, closely followed by ‘adequacy of investigation’ which garnered 543 complaints.
The ombudsman pointed out these figures were for primary concerns only, whereas complainants usually come forward with multiple issues.
‘In our experience, people tend to complain about a number of factors if they are unhappy with how we’ve dealt with their complaint’ and the data does not represent a definitive overview of what these complaints cover,’ said a spokesman.
There were seven further topics for users’ primary concerns for 2015.
The third most common was ‘adherence to FOS process/procedure’ which was top in 236 cases, and the fourth was ‘communication’ in 287 cases.
Nearly 200 of those who complained about the FOS said their main concern was redress and outcome relating to their initial complaint to the service.
Fairness and impartiality was the main concern of 148 complainants and discrimination was top of the list for 15 people.
The FOS annual review states the service investigated 340,900 new complaints in the year to March 2016, and 75% of the resolved complaints were followed with a positive rating from the complainant.