National Australia Bank and Westpac have wasted little time this year beefing up late payment fees on credit cards.A review of movements in late fees conducted by Banking Day in the wake of Maurice Blackburn's failed exception fees test case last year shows that NAB and Westpac have been the most aggressive fee hikers in the credit card market.Only a handful of customer-owned institutions have boosted late fees in the last 12 months, with the most notable being CUA, which has hiked its fee by A$2.50 to $12.50.However, that movement is dwarfed by the NAB and Westpac adjustments, which have boosted late payment fees on most low rate and loyalty cards by 65 per cent.Before the High Court confirmed in July last year that banks were free to collect late payment fees from credit cardholders, NAB and Westpac each charged $9 when customers were late paying their monthly accounts.Today, both banks collect $15 from late paying cardholders.No Westpac customers have escaped the fee hike, with all of the group's subsidiaries - St George, BankSA and Bank of Melbourne - mimicking the higher fee set by their parent.When the High Court handed down its decision more than a year ago consumer advocates were concerned that banks and other card issuers would immediately begin slugging customers with higher fees.But NAB and Westpac appear to have been exceptions to the rule across the industry, with most card issuers electing not to adjust their late fees since the court decision.Macquarie Bank and Woolworths each impose late fees of $35 on late paying cardholders, which Canstar found last year to be the highest in the market.Neither ANZ nor Commonwealth Bank have increased their fees in the last year and continue to collect $20 from late payers.CBA subsidiary Bankwest taps its late paying customers for $25.Perhaps the most surprising finding of our study was that 16 customer-owned institutions continue to levy no fees on cardholders who are up to a week late settling their monthly credit card bill.The list includes Australian Military Bank, Bank Australia, First Option Credit Union, G&C Mutual Bank, People's Choice CU and Summerland CU.