Use the Data Validation + Countif function. It Prevents the user from entering Duplicate data.
To do this:
1. Select a range of cells, for example, A2:A20.
2. On the Ribbon click <Data> à <Data Validation>
3. Select the [Settings] tab.
4. From the Allow dropdown list, select Custom.
5. In the Formula box, enter the following formula:
6. Type an appropriate error message in the [Error Alert] Tab
Do you think CBDT should extend Tax Audit Report and relevant ITR Due Date? Please Comment, Vote, Retweet and Like.— Tax Guru (@taxguru_in) September 18, 2018