Treatment of ITC of capital goodsfor non production period for a starting business

I have supplied both taxable and exempted goods by using taxable input. I have purchased a capital goods during the month of January 2018 but started commercial production and outward supply during the month of January 2019. What is the treatment of ITC of during the period January 2018 to January 2019 specially during the time from the date of purchase to commercial production and outward supply.
(1) For the computation of life period of capital goods whether date of invoice or date of commercial production correct?
(2) If the date of invoice is the right answer, then, is it correct to allow the ITC for the non production period?