Marriage

You should usually file a Joint return which is only 1 return combined for the both of you. 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. Make sure to stick with this one account for the future. Just ignore the other spouse's account.

Getting Married FAQ
https://ttlc.intuit.com/community/tax-filing-status/help/what-does-getting-married-mean-for-my-taxes/00/1756642

Tax info on getting married
https://turbotax.intuit.com/tax-tips/marriage/getting-married/L0DvEUlEC

Did you both use Turbo Tax last year?

You can not transfer from or combine 2 returns or accounts. Just pick the return for the spouse that has the most complicated return to enter or has any depreciation or business or more investments. Or use the account/return for whoever you want to be listed first going forward (by the way you can not change the order of the names). Then add the other spouse's name, ssn and info to it.

But if you want to keep the prior accounts separate from the new Joint account then start a new account. Online is only good for one return per account. But you can use the same email address for 5 accounts.

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

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.

Well congratulations in advance on your upcoming nuptials.   Almost all of the positives and negatives associated with Married Filing Jointly ("MFJ")  versus Married Filing Separately ("MFS") are associated with filing as MFS.   

They include, but are not limited to:

• If you file as MFS, you are often automatically disqualified from the American Opportunity Tax Credit and the Lifetime Learning Credit; the Earned Income Tax Credit (which in your case your incomes exceed the limit of the credit.);  the Credit for adoption expenses; and most likely the Child and Dependent Care Credit. 
• Separate filers usually get a smaller IRA contribution deduction.
• Couples who file separate returns can't take the student loan interest deduction.
• The capital loss deduction limit is $1,500 each when filing separately, vs $3,000 on a joint return.

With the incomes in your questions of $90K and $45K if you used MFS you most likely would pay more overall in taxes.  This is due to the tax brackets for MFS being half of the  MFJ tax brackets.   

Your fiancée if he currently itemizes deductions, since he owns the home, could continue to itemize deductions when using MFS, but you would also have to itemize deductions as well.   

There are two circumstances under which MFS would be better and neither is a tax reason.  The first is separated finances, which are often associated with a pending divorce.  The other is student loan debt.   This is a good article to look at that is a Department  of Education article: 4 Things to Know About Marriage and Student Loan Debt 

Congratulations and best of luck @Lola1234 

All the best,

Marc T.

TurboTax Live Expert

27 Years of Experience Helping Clients