how to add credit card due balance which set up as vendor to the chart of accounts and verdor's bill write off.

Hello, morshed jahan.

I can provide you the information you need regarding writing off the vendor's bill and transferring its due amount in QuickBooks Online. For your first question, you can create a journal entry to write off the vendor's bill in QuickBooks Online.

Here's how:

1. Select + New.
2. Select Journal entry. Or, if you're in Business view, switch to Accountant view first. Then come back to these steps.
3. Fill out the fields to create your journal entry. I'd recommend consulting an accountant. Your accountant can help guide you on which account to debit and credit.
4. Select Save and new or Save and close.

You can get more details about this process in this article: Resolve A/R or A/P balances on a cash basis Balance Sheet.

For your second question, the following write-up contains information on how to transfer the vendor's credit card previous amount: How to enter outstanding balances for customers and vendors.

Also, you might want to check out these articles to for your future references about writing off customer's balances in QuickBooks:

Write off bad debt in QuickBooks Online

Use write off invoices

If I can be of help while working in QuickBooks, feel free to let me know by adding a comment below. I'll be more than happy to assist you.