Transport Scotland's latest performance figures reveal ScotRail has been hit with £687,422 in penalties for falling short of required standards on issues including litter, timetables and toilet conditions at stations, and reservations on board trains.
Despite missing 23 of the 38 targets between April and June, the money withheld from the train operator has fallen for the sixth consecutive quarter and is down from £1,180,571 during the same period last year - a 43% drop.
The Service Quality Incentive Regime (Squire) report assesses facilities at stations and on trains and, when standards fall short of the benchmarks, money from Transport Scotland is withheld from the operators and put into an investment fund used for projects across Scotland's railway.
In the latest Squire assessments, ScotRail-operated stations missed 12 of the 21 targets and its trains fell short in 11 of the 17 categories.
ScotRail's head of customer operations Phil Campbell said: "Everyone at ScotRail is working flat out to improve the quality of our service, and these figures show the considerable impact the efforts of our people have already had.
"The investment in brand new and upgraded trains, better stations and improved infrastructure is delivering the service our customers expect and deserve."
A Transport Scotland spokeswoman said: "These latest Squire results are evidence of the recent positive progress and the ongoing efforts to ensure this continues, particularly around staff recruitment and training.
"While penalties have reduced over six consecutive periods, we recognise there is still work to be done and will continue to press ScotRail to deliver the high standards both ministers and passengers expect and deserve."
Scotrail, owned by Dutch firm Abellio, has had to contribute £12,909,706 to the Squire investment fund since taking over the franchise, according to Scottish Labour.
The party's transport spokesman Colin Smyth said: "The SNP said that Abellio would be a world-leading deal for Scotland's railways, instead the firm has racked up more than £12 million worth of fines since the current franchise began.
"Hard-pressed rail passengers are being continually failed, with the SNP handing Abellio an effective licence to fail, with missed targets and poor performance repeatedly ignored.
"Michael Matheson has the option to strip Abellio of the franchise this year - but it increasingly looks like he has no intention of doing so.
"The next Labour government will end this chaos by bringing our railways into public ownership and delivering a transport system that people can rely on."