Commonwealth Bank was the subject of the highest number of complaints to the Australian Financial Complaints Authority over the year to June, with the other big banks not far behind.Others big-time offenders included ANZ, Suncorp, NAB, Westpac, IAG, Citigroup, finance company Multipli, QBE, American Express, Latitude and PayPal.CBA was way out in front, with 3890 complaints. ANZ, at number two, received more than 1000 fewer complaints.AFCA released its annual report yesterday, reporting that between 1 November last year, when it started, and 30 June this year it received 47,223 complaints. It resolved 67 per cent of them, awarding A$112 million of compensation.Sixty per cent of complaints were about banking and finance, 23 per cent about general insurance, 9 per cent about superannuation, 5 per cent about investments and advice and 2 per cent about life insurance.By product type, credit cards attracted the most complaints (7112), home loans 4085, personal loans 3724, motor vehicle insurance 2680 and home building insurance 1887.The biggest issue was credit reporting (3149 complaints), followed by unauthorised transactions (2927) delays in insurance claims handling (2716), incorrect fees (2477) and service quality (2405).AFCA said the high number of complaints relating to credit reporting reflects the fact that it is often raised as a secondary issue in a complaint about another matter.The large number of complaints about unauthorised transactions indicates a large number of cases involving scams, where the scammer tricks the customer into transferring funds or providing access to their account."The methods used by scammers have become increasingly sophisticated and are designed to overcome a financial firm's unauthorized transaction procedures." AFCA said it saw a large number of complaints about responsible lending in relation to credit cards, personal loans and home loans.Eighty-six per cent of AFCA's 37,488 members did not have a complaint lodged against them. Among its membership, mortgage brokers make up the biggest group, with 2075 members, followed by finance brokers, financial planners, credit providers and accountants.AFCA identified a number of systemic issues (issues that had a wider impact than just the customer making the complaint). These included non-compliance with responsible lending obligations, system errors and inadequate resourcing and handling of internal complaints functions.It referred 24 "possible serious contraventions" to regulators.