If you have a company file on Quickbooks 9 uk version....Now you installed quickbooks 2018 uk and want to add that older version,s company file or restore it How?

I am  not sure you are able to upgrade your file in one jump. But you may try this one. Create a backup file of your company to get the QBB file and (try) restore it on your QBD 2018. If you are failed, find an older version to upgrade your file as a stepping stone. Otherwise, contact us in private to purchase our upgrade service.  

I can share some learning on how to retain your QuickBooks 9 UK version to QuickBooks UK 2018, @mastoroudes22-gm.

QuickBooks version 9 (2009 release) is an old version and is no longer supported. However, you can add the company backup file (qbw9) to versions 2012 (version 12) > 2015 (version 15 is) then to 2018 (version 18) and know some system requirements for older versions. For lower versions, like 9 and 12, you can install and run them with Windows 7 Operating System (OS).

So the process would be to step up the version where you backup and restore the company file until you get into the QuickBooks 2018 UK version. Also, you can still run version 2015 in Windows 10 OS. This way, you can minimize system issues. Please see the System requirements for QuickBooks Desktop 2018.

In addition, you can message our QuickBooks Data Services support if you need some help about upgrading your company file from version 9 to 18. Feel free to read our QuickBooks Data Services FAQs for more details.

If you have other concerns with adding your company file to the newer versions of QuickBooks Desktop, you can always share some time to comment here. I'll get back to you. Take care and have a good day!