rectification of demand by IT Dept.

It seems that you have not filed Returns for preceding 10 years (may be I m wrong).
First of all you should check your 26AS for all those years.
and if you find that it shows regular salary income and TDS thereon u/s 192 then you have to consult your employer regarding this.
If it does not show this, then you may file response to demand that your an pensioner and had not received any salary, with 26AS as proof of it.

1. If you are in receipt of a pension that amounts to salary and it will be taxable according to the slab limits. 
2. If the same is reflected in the 26AS, then it might seem in the eyes of the department that such pension income is subject to tax and you have failed on the same demand notice is possible. 
3. I would recommend you to see the 26AS and consult a professional in this matter. 
Please correct me if the above solution has an alternative view.

here problem is different.paper of IT shows I have received salary even in jan 2019 onwards , but facts is I retired 11years ago.why should I pay tax on amount I never received.yours etc.saurish chakrabarty.