Just remember this.
Whatever SSN you pay with, your payment will be credited to that SSN only.
But when you file your *JOINT* tax return, all payments made by both or either tax filer on that tax return will be applied to the JOINT tax liability.
I don't know if this would be of any help or not. But there's another way to handle it for the 2021 tax year that you might want to consider.
See https://www.irs.gov/businesses/small-businesses-self-employed/filing-and-paying-your-business-taxes for more details on how you can set things up so that each business pays their own quarterly taxes using the business EIN. I do it that way to keep things separate from the personal W-2 income and the taxes withheld on the W-2 income. Not really a requirement, necessity or anything. It just makes my own book keeping between the W-2 income and the SCH C income easier to track.
