Coverage of 'special events' such as the papal visit, the presidential election and FIFA World Cup cost RTÉ €7.2 million last year.
The public service broadcaster's annual report shows it had a net deficit of €13 million in 2018.
RTÉ has described 2018 as 'a challenging year' with a modest €1.5 million increase in total revenue.
Licence fee income increased by €3 million compared to 2017.
However, commercial revenue fell by 1% - with RTÉ suggesting both Brexit uncertainty and changes in media consumption habits impacted the advertising market.
The report also shows that RTÉ had 1,822 full-time or part-time employees on December 31st 2018 - down more than 100 compared to 2017.
Commenting on the report, RTÉ Director-General Dee Forbes said the broadcaster wants to do more - but needs more funding to do so.
She argued: "We are full of programme ideas, but every day we have to curtail our own ambitions and the creative ambitions of the broader independent production sector due to our constrained resources. TV Licence payers want us to do more and deserve more from us.
"However, it will not be possible for RTÉ to maintain and enhance what we do and fulfill our remit without action from Government and a solution to the funding of public service media in Ireland."
Mrs Forbes pointed to reports calling for increases in public funding for RTÉ and reform of the TV licence system - but claimed there has been no "substantial response" from Government.