A contract relating to mobile phone services at Áras an Uachtaráin worth €37,555 did not comply with State purchasing guidelines, the Dáil's spending watchdog has been told.
Martin Fraser, the secretary general of the Department of the Taoiseach, faced questions on the contract as he appeared at the Public Accounts Committee (PAC).
Fianna Fáil TD Bobby Aylward raised the issue after a report on spending in 2017 showed the contract was "rolled over" and did not comply with procurement guidelines.
Mr Fraser is the accounting officer for the presidency, though he has no executive or operational responsibility for Áras an Uachtaráin.
He said that the Áras told him that there were difficulties in relation to the mobile phone signal so they only ever had one service provider.
Mr Fraser said the contract has now been put out to tender and a contract is expected to be awarded next month.
The PAC was examining presidential spending for the first time since its controversial examination of spending just ahead of last year's election, amid claims it could influence the vote.
Mr Higgins's opponents used allegations about presidential spending to attack him during the campaign. Áras spending is now to be routinely examined by the PAC. After the election the President released details of expenditure by his office between 2011 and 2018 and plans to publish updates every year.
Mr Aylward said there were complaints that the information wasn't detailed enough.
Mr Fraser said: "Anybody is entitled to criticise the President, it's just that he's not answerable to the Oireachtas."