The notices required each platform to answer questions about measures they had in place to tackle terrorist and extremist material on their sites.
Telegram and Reddit were also specifically asked about the measures they were taking to combat child sexual abuse material, a topic other services had already been asked about in previous reporting notices.
All other platforms engaged by the May 2024 deadline, but Telegram provided a response five months later and in turn fined $957,780.
Ms Inman Grant said the fine sent an important message to the industry that timely transparency is not a voluntary requirement in Australia, and reinforces the need to comply with the country's laws.
"These powers give us a look under the hood at just how these platforms are dealing, or not dealing, with a range of serious and egregious online harms which affect Australians," she said.
"Telegram took 160 days to provide information that was asked in the reporting notice and providing this information so late has obstructed eSafety from delivering its functions under the Online Safety Act for almost half a year. "
Ms Inman Grant said the threat posed by terrorist and extremist material shared and promoted online posed a growing risk to the community, which is why these platforms need to step up and prevent their services from being misused.
A spokesperson for Telegram said the messaging service had responded to all questions in 2024 with no outstanding issues.
"The unfair and disproportionate penalty concerns only the response time frame, and we intend to appeal," the spokesperson said in a statement issued on Telegram on Monday.
Answers provided to eSafety will be summarised in a transparency report to be released over coming months.
The Australian Security and Intelligence Organisation (ASIO) recently raised the country's terror threat level to probable, citing online radicalisation of young people as driving the heightened threat.
Responses by X will not be included in that report as the online giant fights a fine issued to the platform formerly known as Twitter in October 2023.
The eSafety Commission issued the penalty, alleging Twitter failed to adequately respond to questions about how it tackled harmful content on its platform, including child sexual abuse material.
But lawyers for X argued in the Federal Court of Australia in 2024 the fine had been issued to Twitter which has "ceased to exist" after March 15, 2023 when X Corp merged with Twitter in the US state of Nevada.
Mr Musk registered X Corp in Nevada in early March 2023 and court documents later indicated Twitter had "merged into X Corp and no longer exists as a separate entity".
Twitter, which Mr Musk took over in October 2022, was rebranded as X in July 2023.
