The negative relief is because of following:

1. That I am receiving pension for which after claiming deductions us 80 C , 80 DD and 80 U my tax liability is nil for this AY  2021-22.

2. That I received salary arrears for the AY 2018-19 when I was in active service and this arrear amount was taxable at 30% which has been deducted by the employer as TDS and is reflected in for 26 AS as well as in prefilled ITR on the IT portal along with taxable arrear amount also.

3. Now adding pension for this AY as pet form 16 the arrear amount mentioned above comes under 10 % taxx bracket I.e much below 30 % what was supposed to be paid during AY 2018-19.

What is the recourse?

The negative relief is because of following:

1. That I am receiving pension for which after claiming deductions us 80 C , 80 DD and 80 U my tax liability is nil for this AY  2021-22.

2. That I received salary arrears for the AY 2018-19 when I was in active service and this arrear amount was taxable at 30% which has been deducted by the employer as TDS and is reflected in for 26 AS as well as in prefilled ITR on the IT portal along with taxable arrear amount also.

3. Now adding pension for this AY as pet form 16 the arrear amount mentioned above comes under 10 % taxx bracket I.e much below 30 % what was supposed to be paid during AY 2018-19.

With regards 

What is the recourse?

Simple, when you file your return for AY 2020-21, do not claim arrears u/s. 89(1), but calculate tax liability of the arrears in the current AY. So your tax liability will be in 10% range, & remaining amount you can claim as refund.

What I mean is pay tax as per slab rate in the current AY, even for the arrears amount.

Good Luck ..

Sir if suppose arrears are paid for 10 years back while calculating the relief the tax relief is positive in 8 years is Rs 200000/- & 2 years due to some Capital gain tax the surcharge is applicable so its coming negative in 2 years is coming to - Rs 20000/- so the net relief is coming to Rs 180000/- will be considered or 200000/- will be considered as we have excluded 2 years considering negative ?

But Sir Do we need to revise the Itrs of the respected years to which the arrears belong if the balance comes out to be negative of relief calculation ?