As per 43 CGST : If the Capital Goods Used In supply of both exempted supply & taxable supply , the ITC is to reversed in proportion to Exempted supply
If you use it only for making taxable or zero rated supply, no need to apportion. Entire credit can be utilised instantly. However, if you are using it for making taxable and exempted supply, then, you have to first apportion taking useful life as 60 months and then reverse one month portion of that credit in proportion to exempted turnover.