Hall, 21, played 11 games for the Magpies during a six-month stay at Meadow Lane in 2017-18.
The Seagulls have not included a recall option for the Northern Ireland Under-21 centre-half, who has been at Brighton since June 2016.
"I can't wait to come back. My time at Notts so far has been an amazing experience," he said.
"Meadow Lane is definitely the best place for me right now.
"I feel like I improved so much during my loan last season and I'm really pleased the gaffer [Kevin Nolan] and his staff wanted me to come back."