I have a problem linking task with Invoice

I have a problem linking task with Invoice

Hi Zoho Developer,

I have written a code in php zoho api which create task and assign it to the invoice.
Create task is working fine and its creating task into zoho panel but its not linking with the invoice.

Please find below code:

  1. $crmid = "3051265000001316001"; // customer id
    $realted_to_id = "3051265000003854220"; // invoice id
    $task_data = array(
        'Subject' => "New Invoice - 22", 
        'Due Date' => date('Y-m-d',strtotime("10-10-2020")),
        'Status' => "In Progress",
        'Priority' => "High",
        'CONTACTID' => $crmid,
        'RELATEDTOID' => $realted_to_id,
        'Related To' => "HO000001",
        'SEMODULE' => "CustomModule5001",
    );

    /* Insert Task in zoho */
    $task = $zoho_api->insert_record('Tasks', $task_data);

To link Task with invoice, I'm using two fields 'RELATEDTOID' and 'Related To' but its not linking :(

Please help me on this. Let me know if any other things required.

Thanks