Hi Tracy,
Are you using version 8.0A of Adagio Payables or something earlier? The answer will be different depending on the version in use - importing was greatly improved for this release.
For version 8.0, simply having the Cash Invoice field in the import template is all that is necessary for importing this type of document. If you want to import payments or pre-payments, do not have the Cash Invoice field in the template.
To get a detailed breakdown on the rules for required fields in importing, access the Help file and choose the topic 'Importing and Exporting', then the link to 'Import and Export Format Notes'.
If you are using an older version of Payables, importing cash invoice is performed by setting the Transaction Type field as a value of '1'.
Please note that there are problems importing cash invoices using older versions, namely you are limited to importing a maximum of 10 in a single batch, and you cannot import for miscellaneous vendors (not on file). Both of these have been addressed for version 8.0A.