How can I offer a 3-month free period on my subscription contract?

[sajjadmurtaza]

I have a selling plan

mutation($input: SellingPlanGroupInput!, $resources: SellingPlanGroupResourceInput) {
        sellingPlanGroupCreate(input: $input, resources: $resources) {
          sellingPlanGroup {
            id
            name
            sellingPlans(first: 1) {
              edges {
                node {
                  id
                  name
                }
              }
            }
            products(first: 1) {
              edges {
                node {
                  id
                }
              }
            }
          }
          userErrors {
            field
            message
          }
        }
      }

and with variables

{
        input: {
          name: 'Prime group',
          options: ['Prime'],
          sellingPlansToCreate: [
            {
              name: 'Prime',
              options: '1 Month',
              position: 1,
              category: 'SUBSCRIPTION',
              billingPolicy: { recurring: { interval: 'MONTH', intervalCount: 1 } },
              deliveryPolicy: { recurring: { interval: 'MONTH', intervalCount: 1 } }
            }
          ]
        },
        resources: {
          productIds: "ID"
        }
      }

and i consume webhook to create the subscription contract.

Everything is working correctly.

Now: 

I want to make new changes to have the first 3 months for free billing, After 3 free months, the customer should start paying for a subscription.

If someone can guide how can i achieve that?

https://shopify.dev/docs/api/admin-graphql/2024-01/input-objects/SellingPlanInput

[purvaaerocity]

Thank you for your educational message! Your ability to explain complex concepts in such a clear and concise manner is admirable. Your expertise is a valuable asset to this community, and we appreciate your contributions.Purva Aerocity