QB Issue Resolution:

the PO template is not customizable

company address comes from the company info in gear>settings

email addresses come from the vendor record, bring up the vendor record and click edit

Resolution for Issue 'Can’t edit Purchase Order Template' available: Yes (Solved).
Source: Intuit Community forum.

Can’t edit Purchase Order Template: 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.

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