I married a UK citizen this year, and as he resides in England he does not have a SSN. How can I correctly file my return in this situation?

[DoninGA]

If you are a US citizen and your spouse does not have a Social Security number or an ITIN and you are not applying for an ITIN with the tax return then you can only file your tax return as Married Filing Separately.  Where asked to enter the spouse's Social Security number enter 999-88-9999.  You can only print and mail your tax return, it cannot be e-filed.  When you print the tax return erase the Social Security number for your spouse and manually enter NRA for non-resident alien.

See this TurboTax support FAQ for the procedure to print and mail a tax return using the online editions - https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online

If you wish to file your tax return as Married Filing Jointly you must apply for an ITIN with the tax return and you would need to be providing a statement with your tax return that you want your Nonresident Alien Spouse Treated as a Resident.  See IRS Publication 54 Tax Guide for U.S. Citizens and Resident Aliens Abroad pages 6 and 7 - https://www.irs.gov/pub/irs-pdf/p54.pdf

Go to this IRS website for ITIN information - https://www.irs.gov/individuals/international-taxpayers/general-itin-information

[Opus 17]

Because you are married, you must file as married filing separately or married filing jointly, unless you provide care in your home for a qualifying child dependent. In that case, you may be able to file as head of household.

Joint filing usually has lower taxes in the US because some credits and deductions are disallowed or reduced when filing separately. However, to file a joint return with your spouse, you must make an election to treat your spouse as a US resident for tax purposes and this means that you must report all of your spouses worldwide income and pay US income tax on it, even if your spouse does not live in the US. There is a credit or deduction if your spouse also pays for in taxes on the same income that will reduce the impact of double taxation. 

Therefore, the decision of whether to file jointly or separately is complicated and which is financially better depends on your unique circumstances.  You can create multiple test returns in TurboTax if you have separate online accounts for each test or if you buy and install the software on your own computer.