It really depends. Without seeing your return, it is hard to give a definite answer as to what is going on.
You mentioned, you would both need to itemize? Why is that? Are his itemized expenses over $14,600 and yours are not? How much over?
And when you say itemize, are you talking about things like medical expenses, mortgage interest, property taxes, gambling losses up to gambling winnings or are you talking about business expenses?
If you are talking about business expenses, those are not the same thing as itemized expenses. If he is just taking business expenses, it is possible he is still taking the standard deduction.
If he is itemizing his return and if his itemized expenses are more than the standard deduction but less than the Married Filing Jointly deduction. At the same time, what type of deduction are you taking on line 12 of your 1040? Is it $14,600? If so, then you are taking the standard deduction.
When you combine his income with yours, does it put you in another tax bracket?
One of the best things to do is to write down the numbers on your return separate and do the same for his separate, then see what changes when you file jointly. This will tell you why your refund is not covering his SE taxes.
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