QB Issue Resolution:
If the last invoice was dated in January 2019, you can start with that record. Then, inactivate the estimate in 2018 with a memo stating it was inactivated because you started a fresh company file with 2019 data.
In relation to accounts, users do closing of books to zero out the accounts in the last year and forward the balances in the next year. If we do that to estimates, we can adjust its amount to be $75,000 in 2018 and do progress invoicing and payments. Then, create the remaining estimate worth $25,000 in January 2019 and do progress invoicing and payments. You can add a memo to your transactions. This can be a workaround.
I would highly suggest reaching out to an accountant to get the best advice to properly record your entries. Then, you can always go back to this thread when you have special instructions so we can help you with them.
Lastly, please be sure to back up your company file before touching your records to keep a copy of the original data.
Resolution for Issue 'New File for 2019, managing old Estimates and Invoices from 2018' available: Yes (Solved).
Source: Intuit Community forum.
New File for 2019, managing old Estimates and Invoices from 2018: 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 Company File
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