Remember the forgotten clause of ISO 9001:2015, clause 0.4 Relationship with other management system standards where we can read:
“This International Standard does not include requirements specific to other management systems, such as those for environmental management, occupational health and safety management, or financial management.”
I would be glad if the financial department manager in my company decided to write an SOP, which means more people are aware of the benefits of internal standards to minimize errors and variability. However, I would not include that SOP within the scope of the system. You may even provide a QA code, but in your communication with the certification body, you should clarify that it is outside of your quality management system scope.
The following materials will provide you with more information about documenting a quality management system: