Hello ME,
Welcome to the Community page,
So to write off bad debt in Quickbooks desktop is if you follow the steps below
1. Go to Lists > Item List
2. Create a new Service Item called "bad debt"
3. set the account for this item as Sales (Income account)
4. create a credit note to the customer using the bad debt account you created in the "Item" section
5. set the amount as the amount of the bad debt you want to write off
6. Go to receive payment and choose the invoice, then apply the credit
