To import your invoices, you will need to temporarily turn off the sales tax feature in your account, Kathleen.
When importing a large batch of invoices, the system may apply new tax calculations to your existing data, causing inconsistencies and incorrect totals. To avoid this issue, you can temporarily disable the tax calculation feature during the import process, ensuring your invoices import with the correct, original totals.
Once the import is complete, you can re-enable the sales tax feature to restore your tax settings and resume regular operations.
I've included a resource on importing data that will be useful moving forward: Common questions about importing data.
If there are any additional questions, The Community is just a post away.