This is the most common and MOST frustrating error for our users. 90% of issues pertain to this part so its important that we discuss this in good detail.
Tally ERP9 has a very strict import system. It considers even one extra space as a different character. So "Rajnikanth Ledger 1" and "Rajnikanth Ledger 1" and "Rajnikanth Ledger 1 " are all considered to be different.
Sometimes the extra space is not even an actual space bar space but a line break. This is also considered not to match.
For the import to happen without errors, it is CRITICAL that the ledger names in the entries EXACTLY match the ledger names in the ledger list. There is no other way to do it. Hence this annoying check is there 
Some users have asked if we can just create new ledgers automatically if the ledger does not exist in the current ledger list. This option was considered in great detail but finally the call taken is that it will be wrong to do it as we then run the risk of having many similar named accounts (see the Rajnikanth example above) which will then cause bigger problems for our users in future.
So keep your current ledgers in control and things will be fine. If you have a large number of ledgers to create you can always use the create ledgers template!
Please let me know if the comments if you have faced any issues with this and how you solved them.