We would need a lot more information than that. Some things that affect a refund versus owing is the amount of income, the amount of taxes withheld, the amount of itemized deductions and any credits.
Are you splitting the itemized deductions? If not, then are his higher?
If you can do a line by line comparison with his return to tell you the difference.
Is there a reason you are filing Married filing Separate and not Joint?
Unless you have a specific reason to file separate returns, It is usually better to file Joint. Joint has the lowest tax rates and the highest Standard Deduction. And if you are in a Community Property state MFS gets tricky to figure out. See,
https://ttlc.intuit.com/community/married/help/married-filing-separately-in-community-property-states/01/26030
And How should you file…..
https://turbotax.intuit.com/tax-tips/marriage/should-you-and-your-spouse-file-taxes-jointly-or-separately/L7gyjnqyM?srsltid=AfmBOopGqCNexowW0pYgvsf7ycIkrx4VjO_63UXv6vSnfu3UEGQiKQTh
Here's some things to consider about filing separately……
In the first place you each have to file a separate return, so that's two returns. And if you are using the Online version that means using 2 accounts and paying the fees twice.
There are several credits you can't take when filing separately, like the
EITC Earned Income Tax Credit
Child Care Credit
Educational Deductions and Credits
And contributions to IRA and ROTH IRA are limited when you file MFS.
Also if you file Married Filing Separately up to 85`% of your Social Security becomes taxable right away even with zero other income.