In the GST law there is no separate schedule of classification of goods. Goods are classified based on Harmonize System of Nomenclature (HSN) primarily governed by the customs tariffs Act 1975.
In this context, Notification No. 1/2017-CT(R) and Notification No. 2/2017-CT(R), which practically defines the GST Rate & exemption status for different goods, also mentions the HSN & description of respective goods. These notifications form basis for recognizing the HSN codes of goods of taxation under the GST Law.
The first Schedule to the Customs Tariff Act contains 98 chapters, each chapter covering a different class of goods, and all the chapters collectively are supposed to cover all possible forms of goods. The above mentioned rate notifications in the GST Law include selected tariff heads (HSN Codes) with the specific description of goods which may be slightly different in coverage (at times) than that in the customs tariffs. However, on a broader note, the HSN Codes in the customs tariffs and the GST Law are similar.