You may be in the scenario of having bulk imported your contacts some weeks ago, have built up some contact history and interactions but you now realise that you forgot to link up and import your contact custom field data, but you are nervous of creating duplicate contacts! There is a solution so please read on...
1. Check first that you have created the appropriate contact custom fields / types.
2. Check your ,csv file to ensure that the custom field options are neatly arranged in the correct columns, in readiness for your import.
3. Do all your contacts in your spreadsheet have a valid email address? If yes then proceed to action an import of contacts making sure that you match across the email address field, first name, last name and your custom fields. Then in the duplicate processing section tick Update and leave Email address as the unique identifier. In that way you are updating your custom fields BUT not creating duplicate contacts (which is a good thing!!).
4. If no, that some of your contacts have an email address but others do not then you will have to export your contacts first, which then gives you their Contact ID number in the left column of your .csv file, and then proceed as point 3. BUT this time match the Contact ID field in the top section and then in the Duplicate processing section use Contact ID as the unique identifier.
If you have any further questions about this then contact the InTouch Support desk.