Data migration is almost always a nightmare. There are so many things to keep in mind when you’re going through the process, whether it’s moving records from an external system into Salesforce, or just moving data from one set of fields or objects in Salesforce to another. One of the biggest challenges comes when you’re trying to link associated records. VLookup in Excel is a fantastic tool, but it can sometimes fall short if you have a high volume of data. It tends to ignore case, and with the case sensitive Salesforce IDs, this can go from nightmare to full-on crisis. What can you do to avoid this problem before it becomes an issue? You should use Salesforce’s ID18!
You may not know this, but every record in Salesforce actually has two IDs. There’s the standard 15 character ID you see every time you navigate to a record, and then there’s the hidden 18 character case insensitive ID. When doing data migration, it is always a good idea to have both on hand. If you’re exporting a bunch of records to VLookup in Excel, export both. And if you’re importing a bunch of records and want to keep the legacy ID in case of problems in the future, add a field for Legacy ID15 and Legacy ID18. This way, you’ll always have the tools you need on hand.
-Jared and the Salesforce Guys