I use tags and a query to view different groups of tasks
The tasks are generated as jobs come in, i.e. a checkbox line, I assigned ctrl+T to task edit, so I can add a due date. I make sure to add #freelance so it gets picked up by the query below, and displays in a list on my daily template (ctrl+shift+D for me) so whichever daily note I'm in I can see my tasks.
Then I have another for jobs to invoice, adding #inv to the line manually is simple because the tasks plugin lets you click through from the list, and another for "general" todos, which does accumulate, but not in a single file.
Example query (using community plugin "tasks"):
```tasks
not done
description includes #freelance
description does not include #inv
path includes journal
```