NBN Co will in August downgrade its expectations for homes signing up to super-fast broadband in the 2019 financial year, but insists the rollout will be completed by 2020.

Numbers presented at Telstra's investor day on Wednesday indicate the telco is expecting net one-off NBN definitive agreement receipts of between $1.8 billion and $1.9 billion for the 2018-19 financial year. Telstra and other telcos get payments from NBN as previous fixed-line services are disconnected.

Telstra reduced the amount of NBN definitive agreement one-off payments it was to get in 2017-18 to between $1.4 billion and $1.9 billion, after NBN delayed the rollout of the hybrid fibre coaxial (HFC) network late in 2017. Telstra had previous forecast payments of between $2 billion and $2.5 billion for 2017-18.

NBN Co says the completion of the network is still on track for 2020. Rob Homer

Telstra chief executive Andy Penn confirmed to The Australian Financial Review the telco is expecting NBN to update its corporate plan in August with lower numbers.

"I think the simple point is as a consequence of their cease sale and slowdown on HFC, they have not yet updated their corporate plan for FY19 and beyond," he said.