Can i able to use the customized fields in invoice csv import? Because I can't use my custom fields in sale invoice creation via csv impot. I have only free account.

You can use a 3rd party tool.

I recognize the need to import customized fields into your invoices in QuickBooks Online (QBO) using a csv file, Ragul. I will provide a detailed explanation below to assist you with this task. 

Although the option you're looking for isn't available, I can provide you a workaround by performing box mapping during the import process. After importing, you can add a custom field manually to achieve your goal. 

If you are using QuickBooks Online Advanced, follow these steps to create custom fields:

1. Go to Settings, then Custom fields.
2. Click Add custom field or Add field.
3. In the Name field, enter the name of the custom field, and select the type of data that will be included in your custom field from the Data type dropdown.
4. Choose the category to which the custom field belongs.
5. Select the forms where you want the custom field to appear.
6. Hit Save.

For more detailed information, please visit this link: Create and edit custom fields in QuickBooks Online Advanced.

If you're using QBO Plus or Essentials, you can refer to this link for additional information: Add custom fields to sales forms and purchase orders in QuickBooks Online.

Alternatively, you can use a third-party application for seamlessly importing invoices with custom fields.

If you need further assistance with managing your invoices, feel free to reach out to me anytime, as I am available 24/7.