The figure was disclosed in a Delaware stock authorisation filing, the details of which have since been confirmed by Unity.
Such a fundraise would give the company a $5.96 billion valuation.
Flush with cash
Unity has raised more than $600 million to date. Its last investment round in 2018 netted it $400 million from private equity firm Silver Lake, which at the time valued the firm at $2.6 billion.
The tech company said the funds would be used both as a safety net as it expands, as well as allow early investors and employees to cash out if they wanted.
Prior to that, it raised $181 million in 2016 from DFJ Growth, China Investment Corporation, FreeS Fund, Thrive Capital and Max Levchin.
Unity is reportedly eyeing up an initial public offering, which could take place in the first half of 2020.