QB Issue Resolution:

Yes, unless you have the accountant’s version. They can send you an accountant’s file that you can open and send back from a 2018 version to a 2017 version.  It will warn you that you are updating but it is ok

Resolution for Issue 'Hello, I took a copy of my clients quickbooks but they are using quickbooks desktop 2017 and I have 2018. Do I have to purchase 2017 to avoid the conversion?' available: Yes (Solved).
Source: Intuit Community forum.

Hello, I took a copy of my clients quickbooks but they are using quickbooks desktop 2017 and I have 2018. Do I have to purchase 2017 to avoid the conversion?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for 2018 version
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Error Recovery for 2018 version [Canada]
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