QB Issue Resolution:

there is no way merge company data in QBO – I do not know if there is a third party utility that will do it

you should consult with a tax accountant to insure you do not complicate you life with the IRS. It could be that you have to sell one company to another and prepare a final tax return, or …

Resolution for Issue 'We currently have two separate companies and each company has separate quickbooks accounts. We are merging the two companies into one soon. Can I take all of the data from one company account and merge it to the other company account?' available: Yes (Solved).
Source: Intuit Community forum.

We currently have two separate companies and each company has separate quickbooks accounts. We are merging the two companies into one soon. Can I take all of the data from one company account and merge it to the other company account?: 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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