Imported transactions will generally be to a specific account in your account tree. In the following this will be referred to as the import or base account. It may or may not be specified in the data being imported, depending on the import format. It is usually the first split of a transaction being imported.
All transactions will also must have a destination account for at least matching splits. This may or may not be supplied in the imported data. If it is not, an account can be assigned on the basis of the previous import history by matching to infomation in the imported data. The user may always over-ride this assignment.
Multi-split data previously exported from GnuCash may have both the import and destination accounts for transaction splits specified in the data file.