7. As subject goods were 'intended to be used for business' by the tax-payer at the time of purchase, ITC availed earlier can NOT denied afterwards just because such goods are returned back to the original supplier after three years.
W.r.t. my reasoning about the words 'used or intended to be used' used in Section 16(1), kindly refer to elaborate discussion we had under Issue-Id: 118820 having subject-line as SEC 17(5)(h).
Based on the query raised, I am presuming that situation warranting blockage of ITC u/s 17(5) does not exist here and query raised is with regards to Section 16(1) & not Section 17(1).
Issuance of credit-note u/s 34(1) is optional for the original seller. As time-limit to disclose the credit-note (for basic amount as well as GST originally charged) & use 'gst charged earlier' against fresh liabilities u/s 34(2) is lapsed, original supplier should not issue credit-note u/s 34 but 'commercial credit note' for basic value (i.e. excluding GST) can be issued for accounting purpose between parties. This is assuming that subject transaction is indeed 'purchase return' as mentioned in the query.
Alternative Scenario:
As goods were kept by the purchaser for three years, it is presumed that 'sale' took place and goods were unconditionally accepted by the buyer in the year of initial purchase itself. In other words, original seller is not under any legal obligation to take back these goods after three years. And if so, returning these goods now after three year cannot be called as 'Purchase Return' per se but same will be sale (i.e. resale) transaction. In other words, if my presumption holds good factually, this is not a situation where any credit-note u/s 34 can be issued. And in such a case, tax-payer can raise tax-invoice while re-selling goods and buyer (i.e. original seller) can avail ITC against gst charged at the time of re-sale. This alternative scenario depends upon 'facts' involved which only both parties to the transaction should be aware of and same should not be used blindly across every situation.
These are ex facie views of mine and the same should not be construed as professional advice / suggestion.