Should my wife and I file jointly or separately? 5 dependants to claim

Joint filing almost always gives you a better refund or less tax owed, because many deductions and credits are reduced or disallowed when filing separately.  However, the only way to know in each person's unique situation is to test it both ways.  Remember that when filing separately, you must both itemize deductions or both take the standard deduction.  It is not allowed for one spouse to claim all the itemized deductions and the other spouse claim the standard deduction.  If one spouse claims all the itemized deductions, the other spouse must also itemize and claim zero deductions. 

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.  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.  

Many people think they come out better when filing Married Filing Separate but they are probably doing it wrong.  If one person itemizes deductions then the other one must itemize too, even if it's less than the standard deduction, even if it is ZERO!  

And 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.

See …….

https://ttlc.intuit.com/community/married/help/is-it-better-for-a-married-couple-to-file-jointly-or-separately/00/25590