---

@FRANZ wrote:

Is there a penalty If the couple are NOT using the same deduction (standard/itemized)?

---

Why would this even be relevant?  As tax professionals, we all have a duty to prepare complete and accurate returns, whether or not we are credentialed.

But since you asked the question, for a start, you are looking at the standard deduction being disallowed under §63(c)(6).  With that will come P&I for underpayment, at the very least, unless it's caught when the return is processed and there is already sufficient withholding/ES-tax payments to cover the balance due.