Hi @Usman_Tahir –
When a masspayment job completes, it will have created individual transfers for each of the successful items in the masspay. We recommend parsing through the masspayment items and finding which items were successful and which ones failed.
For the failed items, you can try correcting the issue and re-initiating one off transfers for just those items.
For the ones that were successful, they will create individual transfer resources. We recommend storing these transfer IDs in your database to match it with the transfer-related webhooks that will follow (as shown in your webhook example above).
The transfer related webhook itself or the transfer resource do not have an indication of which masspayment they belong to. Although, we have logged this down as a feedback item for our Product team to consider!
Hope that helps! You may also check out this post for information - Mass Payments - Pay 5,000 People in Five Simple Steps