The former finance secretary quit on the eve of the Scottish budget on February 6 after it was revealed he had pestered a 16-year-old boy with messages.
It was reported he sent the school boy 270 messages over six months and even wrote one calling him “cute”.
In the months since he resigned, Mr Mackay has continued to claim expenses.
Much of the money has been spent on rent for a property in Edinburgh, although Q2 figures – which take in July to September 2020 – only include expenditure of £327.10 on rent and £204.50 on factoring costs.
The £327 figure represents the last time Mr Mackay claimed rent for his flat in Edinburgh and was revealed by the BBC in October.
The most recent figures also include £1,125 claimed for office rent, £119.40 for mailing costs, £67.50 on office service charges, and £21.20 on trade waste.
Across February and March he claimed £1,990 for two months’ rent, and the same amount in April and June, with £663.50 spent on council tax.
His April to June expense claims also include £1,125 for office rent, and £344.10 for miscellaneous office costs.
More than £800 was also claimed by the MSP for utilities and trade waste costs for that period, which was not previously included in the figures released by the Scottish Parliament.
He issued a statement at the time of the scandal, apologising "unreservedly" to the boy.
Police later concluded there was "nothing to suggest that an offence has been committed".
In response, the Scottish Conservatives called for the SNP to publish their internal investigation into Mr Mackay and to back the so-called ‘Mackay’s Law’.
MSP Graham Simpson said: “The way Derek Mackay has treated both his constituents and Parliament since this scandal broke has been nothing short of a disgrace.
“The SNP machine chose Mr Mackay as a candidate and let him rise to such dizzy heights, even talking up him as a future first minister.
“People in the SNP must have known about his behaviour, so they must now come clean about their internal investigation into him and share their conclusions.
“Police Scotland finished their own inquiries months ago, so the SNP have no excuses to delay. They’ve had more than enough time for their probe.”
Mackay’s Law would see parliamentarians unable to access expenses should they stop working as MSPs while remaining in position.
Mr Simpson said: “The legislation will stop MSPs benefiting from taxpayers’ money if they don’t do the job they have been elected to do and punish politicians who unofficially give up on their duties, like Mr Mackay.
“The SNP risks undermining public confidence in elected decision makers permanently if they fail to support Mackay’s Law.”
A spokesperson for Mr Mackay said: “All expenditure complies with Scottish Parliament rules and Mr Mackay and his office are continuing to provide a constituency service, having directly assisted in more than 830 cases on behalf of constituents during the last 12 months.
“Accommodation costs included in the second quarter of 2020/21, as previously stated and reported by media on October 1, 2020, covered the notice period and requirements of terminating the tenancy.”