An invoice is a sale, there is no partial sale

if you are asking about a partial estimate being copied to an invoice, QBO can not do that

you have to duplicate the estimate, delete or edit what is not be moved to an invoice, and create the invoice

then edit the original […]

Resolution for 'already invoiced issue: 'How to record partial invoice of sales?' available: Yes.

The already invoiced 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 already invoiced issue yourself by looking for a resolution described in the article. If it is a complex already invoiced issue or you are unable to solve the issue, you may contact us by clicking here or by using other already invoiced support options.

For more information about resolving issues related to already invoiced in Quickbooks/QBO or to get support for the issue 'How to record partial invoice of sales?', click the link below: