What are main steps involved in estimating national income by expenditure method? 

Steps involved. Expenditure method involves the following steps.
(i) Identification of economic units incurring final expenditure, e.g., household (or consuming) sector, firm (or producing) sector and government sector.
(ii) Classification of final aggregate expenditure into following components.
1.    Private final consumption expenditure.
2.    Government final consumption expenditure.
3.    Gross fixed capital formation.
4.    Change in stocks.
5.    Net exports.
By summing up all the five components, we get GDP at MP. or GDP =C + I + G + (X-M).
(iii)    Measurement of final expenditure on the above components. Sum total of final expenditure on the above five items gives us the value of GDP at MP. By deducting depreciation and net indirect taxes from GDP at MP, we get NDP at FC.
(iv) Estimation of net factor income from abroad which is added to NDP at FC (Domestic Income) to obtain NNP at FC (National Income).