Sony recently started an offer that urged PlayStation Store users to spend $100 in order to get $15 back. The offer applied to pre-orders and PS Plus subscriptions and launched near the release of Horizon Zero Dawn.
If you have available the promotion and spent exactly $100 or more, you can now claim your free $15 credit by either checking your PSN emails or accessing the announcement of the free credit code directly from the PS4, as seen below.
The codes that are sent have to be redeemed before March 31st so make sure that you redeem your personal code before it is too late. The code adds $15 wallet balance to your PSN account which you can use to buy games from the recent Batman sale, or wait for the upcoming Flash sale.
Let us know if you have received your free PSN credit code from Sony in the comments below.