In order to change the payment date, you are required to directly apply a trial to the customer's subscription within Stripe. Please follow these steps:
Navigate to the customer's Stripe page and select Update subscription.
On the next page, scroll down to the section titled Free trial days. Here, you will see an option to Add trial days.
When you click on this, a pop-up window will appear in which you can select how many days you wish the trial to be active.
Select the appropriate number of days until you want the next payment to come out. This will reset the payment date moving forward.
Note: Please ensure to turn off prorate charges and that the reset billing cycle is unchecked.
If, for example, you choose to add a 20-day trial, the Summary section will show that the next invoice due on the previous renewal date will be £0.00, and the trial will end in 20 days.
Click on Update Subscription to confirm your choices.
You can then view the upcoming invoice to ensure the details are correct.