For Indonesia and Philippines:
You can refund a Paylater transaction using Refund API.

Here are the steps on how to create PayLater refund charge:

1. Create secret API Key on your dashboard
Reference can be found in this doc.

2. Set your callback URL in Dashboard > Settings > Callbacks in PayLater payment status and make sure upon "test and save" it returns 2XX

3. Create Refund PayLater Charge using endpoint:

POST https://api.xendit.co/paylater/charges/{id}/refunds

The {id} is in plc_ format which is the response you get after paylater charge creation or you can get the id in the Transactions Tab by clicking the transaction.

4. Input you secret API key in Authorization

5. In Body Request you can leave it blank or add parameter "amount" if you wish to be partial and "reason".

6. You will get this response afterwards:

{
"id": "plr_17f6cb16-c1d2-42e4-ac8c-feeb26f20bc4",
"charge_id": "plc_b907ce2b-6817-483a-86e3-fdc8c9c01b21",
"channel_code": "ID_KREDIVO",
"currency": "IDR",
"amount": 1000,
"reason": "",
"status": "PENDING",
"created": "2023-04-04T06:59:12.586Z",
"updated": "2023-04-04T06:59:12.586Z",
"failure_code": null
}

7. You will then receive a callback of the successful refund where you can check on your callback tab.

8. The refunded transaction transaction will appear in Transactions Tab as "refund".

Further information can be checked below:

1. Refund Docs

2. PayLater Refund API