Hra mismatch in form 16 and 26 as, intimation received (143)

Hi,

I have received an intimation under section 143 A for mismatch of income declared while filing return vs income declared in form 26 AS. On checking, I found that form 16 given by my employer mentions the gross amount ( same as amount mentioned in form 26 AS), exempted amount for HRA and the net after deduction.

Why could there be a difference in form 16 and 26 AS, is it a mistake on the employer's end? Should I contact my then employer to correct the form 26 AS record in that case?

Should I mention this in my reply on income tax website e proceedings, while choosing disagreement option for the demand?