OECD guidance – By itself, treatment under VAT/GST is irrelevant for the purposes of the interpretation and application of the definition of permanent establishment in the Convention; when applying that definition, one should not, therefore, draw any inference from the treatment of a foreign enterprise for VAT/GST purposes, including from the fact that a foreign enterprise has registered for VAT/GST purposes.

http://www.dbriefsap.com/bytes/Dec2017_2.2017UpdatetoOECDModelTreatyandCommentary.pdf (page 81)
 
India does not agree with the view expressed in paragraph 5 of the Commentary on
Article 5 that by itself, treatment under VAT/GST is irrelevant for the purpose of interpretation
and application of the definition of permanent establishment. India considers that treatment
under VAT/GST can be a relevant factor for this purpose