Hi there, @whkor.
Let me share insights about combining two different Tax ID.
As a sole proprietor filing a Schedule C your social security number will be on Form 1040 for the individual side of your income taxes.
Combining two Tax IDs in QuickBooks Self-Employed is unavailable. One subscription is equal to one business. You might want to use another QBSE subscription for the other tax ID.
If you want to combine two accounts, I'd suggest reaching out for a Tax Advisor for clarification.
Also, this article can be helpful: Small Business and Self-Employed Tax Center.
You can mention my name if you need further help. Take care.
