In Stripe, create a coupon and select the desired discount, then under 'Duration' choose 'Forever' or 'Once,' and apply it to the specific annual plan ID, ensuring it doesn't apply to monthly plans by not including those IDs in the coupon setup.
@toddt_00 One of my products contains two prices (monthly subscription and annual subscription), and I can only select this product (applied to both annual and monthly prices), I can't select the annual price for this product alone.