When you are in the bill, down the bottom there is an attachment area, just click on the box and attach your supplier invoice and press save.
Resolution for 'attach a suppliers issue: 'I want to attach a suppliers invoice to a bill' available: Yes.
The attach a suppliers 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 attach a suppliers issue yourself by looking for a resolution described in the article. If it is a complex attach a suppliers issue or you are unable to solve the issue, you may contact us by clicking here or by using other attach a suppliers support options.
For more information about resolving issues related to attach a suppliers in Quickbooks/QBO or to get support for the issue 'I want to attach a suppliers invoice to a bill', click the link below: