Addition done by cpc under 143(1)(a) holds valid after 143(3)

Additions made under section 143(1)(a) is summary assessment which permits to make additions when there's mismatch between the data reported by reporting entities and the data filled by assessee. once, addition is made under 143(1)(a), the total income computed under 143(1)(a) would be your total income. in 143(3) assessment, additions can be made in addition to the additions made under 143(1)(a)

A return of income or loss has been made under sec 139 pr in response to a notice under section 142 )1)

It has been done under 139(1). CPC has processed the same. After that it is selected for scrutiny

Scrutiny assesment is seperate...