Need for indemnity bond while responding to outstanding income tax demand

While responding to outstanding tax demand under option rectification/revision filed at CPC, in addition to putting e-filing acknowledgement number, I have to upload 4 things.
1. Challan copy
2. TDS certificate
3. Letter requesting rectification copy
4. Indemnity Bond

Kindly advise on what is the need and format for  “Indemnity Bond” while reponsding to an outstanding demand ? I have to do this online, as my jurisdictional AO is in another state and I cannot visit him personally.