An independent investigation into the telco's July 8 network failure, which left thousands of Australians unable to make calls or access data, was released on Tuesday.
The outage sparked chaos with triple-zero calls and businesses affected, along with failures across train networks and electronic payment services.
A lack of ownership and oversight of the functions that led to the outage were identified as key contributing factors by Technology Audit Partners in the report.
The investigation also found a further eight triple-zero calls did not go through to emergency services during the outage.
The outage began at 2.50am, nearly an hour earlier than identified by the Telstra at the time.
Following the outage, Telstra confirmed it had conducted welfare checks on those who tried to place more than 600 unsuccessful emergency calls.
Since identifying the further eight unsuccessful calls, welfare checks had also been conducted with no adverse outcomes identified, according to the company.
The outage was triggered by a software update not being done on a GPS card, which resulted in incorrect date information.
It was primarily a result of a Telstra not treating network timing as a critical capability, the report found.
On the night of the outage, the two primary engineers involved in the botched upgrade were on mandatory stand-down, the report found.
"The overarching finding is we did not prioritise our timing system inside our networks at the highest level as a critical capability, which is exactly what it should have been," chief executive Vicki Brady told media on Wednesday.
"That is a miss on our side."
Ms Brady said additional resources and expertise had been allocated to the impacted area.
Since the outage, just over 30,000 customers have contacted the telco which has processed credits of just under a million dollars for those customers.
Any customers who felt they were impacted and had not been in contact were encouraged to reach out to the company.
Ms Brady was among 10 senior executives whose pay was cut as a result of the outage, taking her total compensation to $6.8 million, 11 per cent more than the previous year.
"I fully accept the board's decision on that," Ms Brady said.
A separate ongoing Australian Communications and Media Authority  investigation into the outage could result in fines of up to $30 million.
"From our perspective, it's far too early to reach any conclusions or estimates about what potential breaches or fines might look like," Ms Brady said.
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