Based on current records we have in HubSpot?
When importing contacts they are deduplicated based on email address so be sure to include email as one of the columns and map emails during the mapping step: http://wizard.import2.com/docs/hubspot-mappings.
Hubspot will use the company domain name property to deduplicate companies. Upon import, the Hubspot will look at the values for each company’s company domain name property, as long as they match each other exactly, and form a valid URL. If a Company Domain Name is not included in your database the companies will not be de-duplicated.
Also here if you want companies to be deduplicated automatically while importing be sure to map the company domain name while setting up the import.