Step 1: Background of demonetization in India
On 8th November 2016, the Government of India announced demonetization of high-value currency notes of ₹500 and ₹1000.
Step 2: Reason for demonetization
The move was aimed at curbing black money, counterfeit currency, and corruption. After this announcement, ₹1000 notes and old ₹500 notes ceased to be legal tender.
Step 3: Correct year
Thus, ₹1000 currency notes were declared invalid in the year 2016.
\[
\boxed{2016}
\]
Match List-I with List-II
