Intimation 143(1)a wrong head

dear experts,
one of our client had is received rental income of Rs. 28L. for which Tds is deducted for AY 17-18.
while filing return u/s139(4) he declared the rental income as under the head of "income from other sources" for Rs. 12L. department issued assessment order in 19/3/2019 including the income of " RENTAL INCOME" Rs. 19+L.
client ignored the intimation order.

now department issued demand of Rs. 7.39L.
ITO had informed client to pay 20% of demand and go for appeal.

my query is...

any possibilities of going for appeal?
if possible, please mention under which section?

thank you in advance..