Talking to the BBC, Dido Harding said the one off cost will be between £30 million and £35 million.
Costs included TalkTalk’s response to the hack, the extra calls into its call centres and extra IT and technology costs.
The hack has also cost the provider sales because its online sale sites only came back up this week.
But Harding said that despite the hacks the company is in line to meet its targets for its full year financial results.
TalkTalk is offering free upgrades to its customers. It revealed last week that only 157,000 customers had their personal details stolen.
Initially it believed that number could rise into the millions.
Four young men have been arrested as part of a nationwide inquiry into the hack and have been bailed.