How to send subscription notification with Task.ID

We work on FHIR PAO DME and per workflow it looks like we need to send notification to Performing Provider with (

While reading documentation I also see that notifications don’t support body -

When a resource is created or updated that meets the criteria, the server sends a POST request with no body to the nominated URL. 
When the subscriber receives a POST to, it re-issues the criteria as a query to the server, appending &_since=:last (where :last is replaced by the time at which the client last checked). In this way it can fetch all new relevant Observations. 

where should we send, so then performing provider can pull details only for this particular task?

Thank you

I am not familiar with the PAO IG, but this has been addressed generally via topic-based subscriptions in FHIR R4B and R5.

For R4B, details can be found in the Subscriptions R5 Backport IG. For R5, details can be found on the Subscriptions Framework Page.

Again, I am not sure how the new mechanisms interact with the PAO IG, but I hope this helps.