Relief u/s 89 not taken by cpc in intimation

A government teacher has filed itr taking relief u/s 89 in his itr 1 , however cpc did not take the same in tax computation u/s 143 so has raised tax demand on intimation , how shall i file rectification request, either online or manual since how will i attach proof of of relief u/s 89 upon online rectification , since his form 16 is hand written . plz help it on urgent basis