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In order to update the data in bulk, you will have to download it first. If you would like to update the Organisations you have to go to the Organisations tab, tick all or just a few chosen organisations and download CSV file as shown below.
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After you will open up the CSV file you will see all of the organisations. You will see that the 'action' column now has U instead of C. This is correct as now you want to update the CSV file.
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If you would like to update the Contacts you have to go to the Contacts tab and click on Download in on the right top side of the contacts page as shown below. Once again, you will download the CSV file that will need to be updated - you only changing change details that need updating and re-upload again.
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