Demand order against Section 234B

Dear Sir/Madam,

 My client received demand order against Sec 234B.

In my client case , She is Senior citizen and has  Rental income , PGBP ( But Exempt Income -under  Partnership firm) ,CG and other Income.

and exempt income are not part of total income so.

Even though she is Senior citizen paid 87.5% of Advance tax .

as per above Case, give some suggestion.