Unfortunately, you cannot pay the difference amount by deducting your wife's amount. You would have to make a payment with your full owing amount.
If you cannot pay your tax owing balance at once, you can arrange a partial payment.
As per CRA: If you can only make a partial payment, you must also make a payment arrangement to pay the balance of your debt. A payment arrangement lets you make payments over time until you have paid the entire debt, including interest.
For more information, please follow the CRA link provided below:
Paying your 2020 taxes owing
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