A vendor bill lists the quantity received for each line item on the purchase order. In the Vendor Bills form, you can record vendor bills for payment by entering the vendor, items, and expenses. Vendor ID: ID of the vendor for whom the vendor bill is to be created.
Open bills mean bills with not paid or overdue status. If the bill is approved, the status will be opened.
The bill will be closed when the customer pays the amount.
Screenshot for the open bill

OPEN BILL – CSV IMPORT
We can import all open invoices using import assistant. For that navigate to Set Up > Import/Export > Import CSV records.
- Select Import type as ‘Transaction’.

Choose Record Type ‘Vendor Bill’.

- Select the CSV file that wants to import. Then click next.
- In the import options, select Add and click next.
- Next field mapping page will appear. Here map the appropriate fields in the import file with the NetSuite field. Location and currency is a mandatory fields for Vendor bill field mapping.

Click the pencil icon near the Customer’s internal id and select choose reference type as “Internal id”. The same will do for the Item Internal id.

- Click next.
- Save mapping and start import page will appear, give import name and click save and run.

Now the import has been saved. View the import job status.

We can see the import status. On the job status page, if the status is complete the import is completed. Either import is successful or unsuccessful. There is a chance to occur an error.

Download the CSV response file and view the status. ‘All records imported successfully’ means there is no error. If any error occurred, correct it according to the error and import it again.