The company said up to 46.5 million new shares have been placed, worth 5% of its share capital, at 400 pence per share, a 8.9% discount to Monday's closing price.
"This equity raise will allow the group to resume its existing capital return policy at the earliest prudent opportunity," said the company, which has halted share buybacks and remained undecided about 2020 dividends.
Auto Trader also said its entire board has offered to forego at least half of their salaries and that it will furlough its employees.
Shares of the company were down 9.5% at 397.6 pence as of 1154 GMT.
Before the lockdown in Britain, Auto Trader had allowed auto retailers to advertise their vehicles on its website free of charge throughout April, leading to a record number of cars being displayed on its platform.
The FTSE 100 company said it expects to meet its covenant tests in March, but sees the September test showing an increase in its net debt to core profit ratio due to the free services provided.
Auto Trader expects the ratio to remain below the maximum threshold agreed with lenders at that point, however.
It had drawn on 289 million pounds of its 400 million pound revolving credit facility at the end of February, it said.
(Reporting by Yadarisa Shabong in Bengaluru; Editing by Shounak Dasgupta, Bernard Orr and Jan Harvey)