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How to prevent duplicate entries in a column in Excel?

As we all known, Data Validation is a very useful feature in Excel, you can use it to create drop down list in a cell and limit the values user can enter. But sometimes you may want to prevent users from entering duplicate values in a range of worksheet. How could you avoid duplicate entries in Excel?

Prevent duplicate entries with Data Validation feature

Quickly prevent duplicate entries with one click

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arrow blue right bubblePrevent duplicate entries with Data Validation feature


For example, I am entering identify card number into a range of cells (A1:A20), and I want to make sure all item numbers entered in range A1:A20 are unique. To prevent duplicates, follow these steps:

1. Select the range of cells that will contain the item numbers.

2. Go to Data > Data Validation > Data Validation. See screenshot:

doc-prevent-duplicate-entries1

3. And a Data Validation dialog box will display. Click the Settings tab, then click drop down list under Allow, choose Custom, and then enter this formula “=COUNTIF($A$1:$A$20,A1)=1” into the Formula box. See screenshot:

doc-prevent-duplicate-entries2

4. And then click Error Alert tab, under the Title box, enter “Duplicate Entry”, and enter the proper message in the Error message box, such as “The value was already entered. All Item Numbers must be unique. Please try again.”

doc-prevent-duplicate-entries3

5. Click OK to finish it.

Now when you enter a duplicate number, Excel will prevent the entry and alert the user with an error message, it will show up like this:

doc-prevent-duplicate-entries4


arrow blue right bubbleQuickly prevent duplicate entries with one click

It is somewhat difficult for us to use Data Validation function to prevent duplicate entries, now I will introduce you an easy and quick way to solve this task.

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With Kutools for Excel, you can prevent duplicate entries with one click. Please do as this:

1. Select the range that you want to prevent duplicate entries.

2. Click Kutools > Prevent Duplicate Entries, see screenshot:

doc-prevent-duplicate-entries5

Now when you enter the same data with the first data in the range, you will get the following warning:

doc-prevent-duplicate-entries6


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Comments (33)
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This comment was minimized by the moderator on the site
Good and useful tips.
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Usefull tips ! Thanks for sharing
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Thank you so much :)
This comment was minimized by the moderator on the site
Duplicate entry still allowed for copy and paste.
This comment was minimized by the moderator on the site
This formula is okay but when I'm write same word they show me Duplicate Entry & if i 2 same word fill mean Copy paste (Ctrl+C/Ctrl V) 2 same word then can't show me Duplicate Entry Erorr
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[quote]This formula is okay but when I'm write same word they show me Duplicate Entry & if i 2 same word fill mean Copy paste (Ctrl+C/Ctrl V) 2 same word then can't show me Duplicate Entry ErorrBy Sameer Awais[/quote] :roll: It cannot prevent duplicate entries from entering as Copy and Paste.
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Thanx for this useful formula
This comment was minimized by the moderator on the site
Thanks!!! save my day...
This comment was minimized by the moderator on the site
WHEN I COPY PASTE THE DATA IT NOT WORKING ... PLEASE HELP ME
This comment was minimized by the moderator on the site
Thank You Very Much "For This Formula"
This comment was minimized by the moderator on the site
thank you, nice information to study
This comment was minimized by the moderator on the site
This formula for some reason doesn't work for named range in Excel 2013. In example, I have a whole A column but the header, i.e. $A$2:$A$1048576, named as 'id'. The formula =COUNTIF(id,A2)=1 correctly gives TRUE or FALSE when used in other cell for test, but it doesn't affect the data validation - it allows duplicate entries. However when used directly =COUNTIF($A$2:$A$1048576;A2)=1, it works for validation as well, giving exactly the same results in other cells.
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Nice Tips.... Keep Updating....!
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I have done these steps, however... no matter what I put into the column it says it is a duplicate even thou it is not. I have a column that has a header of "P.O.#" I want to prevent from billing more than once for a po.
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It did not work at first but after I unchecked the "ignore blank" box next to custom it worked. Very helpful. Thank you.
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thank you sir, very useful and appreciable :-) .
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[quote]thank you sir, very useful and appreciable :-) .By Rajendra Singh Rana[/quote] I can't entry any data after applying this method ...
This comment was minimized by the moderator on the site
122 314 441 EXL/112/15-16 264 EXL/113/15-16 EXL/314/15-16RY HOW CAN AVOID THIS KIND OF DUPLICATE VALUES DURING NEW ENT
This comment was minimized by the moderator on the site
122 314 441 EXL/112/15-16 264 EXL/113/15-16 EXL/314/15-16 how can avoid this kind of duplicate values during new entry in excel
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unfortunately this formula is not working, it is showing alert when am entering duplicate value, i am using this formula for email id column. Please suggest me.
This comment was minimized by the moderator on the site
Please Help, How can I put a duplicate entry of values? I want to get a warning once I repeat a number 5 times. NOT ONLY TWICE BUT 5 TIMES. My limit is 5 times. please HELP HELP!!!
This comment was minimized by the moderator on the site
Hi Joseph I think Your requirement is very simple, plz try this.... "=countif($A$1:$A$10)
This comment was minimized by the moderator on the site
Hi Joseph Plz try this..... "=countif($A$1:$A$20,A1)
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thanks alot for the tips, but need your more help as i am working on sheet where i have to record the name of the trainees of the year 2015, so not to train the same trainess again 2017 i have to design the database which shows me the duplicate name by highlighting it, so please help me with it.
This comment was minimized by the moderator on the site
Hi Baseer Plz select both data 2015 and 2017 and follow as below.... Home->conditional Formatting ->Highlight Cells Rules->Duplicate Values... Click on OK. Duplicate names will be highlighted.
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