With Thread, you can issue a quick bill with a set value without including any time records in a bill.
1). Enter the matter name you want to create the bill for.
2). This field will automatically populate with a bill name. You can amend it by typing in a new name.
3). Enter the bill amount.

You can edit the bill to include other activities, but the total bill amount will remain as you entered when creating the quick bill.
4. Follow the steps here to issue the bill and generate the bill document.