ice cream manufacturing unit.. composition

Section 10(2) restricts the person, to opt for composition levy,engaged in manufacturers of ice cream

you cannot avail benefit of composition. you need to register as normal tax payer provided your turnover exceeds 20 lakh limit

Ice Cream Manufacturer's are not eligible to opt for the Composition Scheme under Section 10 of the CGST Act 2017.
Register as a Normal Taxpayer if your annual Turnover exceeds the said threshold limit.

Sir, one customer taken composition scheme and returns also filed, i cannot understand how did system accepted the composition scheme. Now what we do.

But as per the Provision of Section 10 (2) clause (a), Ice Cream Manufacturer's are not allowed to opt the Composition Scheme.
Maybe the dealer ( ice cream manufacturer) who have opted for the Composition Scheme, as you said, may not have furnished full information regarding the nature of his business and that is why the system has accepted his registration under the Comp Scheme.

I personally would suggest you to opt as a REGULAR TAXPAYER in the GST REGIME inorder to avoid any type of future problems and harassment from the Tax Authorities.

I agree with above explanation if department comes to know about this they will issue show cause notice for cancellation of composition scheme and they impose penalities.

Sir, Why are ice cream manufacturers kept outside the ambit of composition scheme under the GST?

If Ice Cream contain Cocoa, manufacture  not eligible for Compositions otherwise  Ice Cream Manufacture legible for Compositions scheme.