If you’re already a PlayStation Plus member and thus can’t take advantage of the current deal that nets you some PS Store credit, how about a PlayStation Now subscription instead? Sony is currently running a very similar promotion for its streaming and download service whereby those who sign up for the first time will also be granted £15 of credit to spend in the PS Store. The deal is available until 10am GMT on 23rd March 2021, and a 12-month membership must be purchased in order to qualify for the bonus PS Store credit.
Source: N4G PC New PlayStation Now Subscribers Get Free PS Store Credit