Importing Invoice detail from other QBO that contains two custom fields & 'service date'. Already synced layout same as old QBO, But don't see them in mapping upload

Let's perform some troubleshooting steps to import your custom invoice with the custom fields, coreadviz.

When importing the custom form styles for your invoice, let's make sure we use the angle brackets (<>) for elements on your template. This will show in the mapping upload section for you to map the custom fields/service date in QuickBooks Online (QBO) fields.

Also, check also for angle brackets for the custom fields if they are applied correctly. Then, reduce the fields marked with brackets and add them back in one at a time to avoid the mapping error.

Once done, import the invoice in QBO again by following the steps in this article: Import custom form styles for invoices or estimates. Then, proceed to Import your custom form style section.

In case you need to import multiple invoices in the future, see the Import multiple invoices at once article for the steps and details.

I've got a link here that provides you with articles about managing your customer transactions: https://quickbooks.intuit.com/learn-support/manage-customers-and-income/misc/02/uk-manage-customers-and-income?label=QuickBooks%20Online.

Fill me in if you need a hand with creating recurring transactions or any QBO related. I'll be here to ensure your success. Take care always.