You can not file as single if you are currently married. If you are separated you can only file as separated if you have been separated for 90+ days prior to Dec 31, 2017.
I want to file separate from my spouse. I do not want the spousal deduction.
Unfortunately, if you are married you will have to file as married to prevent an audit. If your spouse has an income >$25k annually you will not receive a spousal deduction.
My husband is a US citizen and he files his income tax in the US. Why do I get a spousal credit for him?
In this case you still need to file as married, however you need to indicate that your husband is a nonresident. Since your husband does not have a Canadian SIN enter 000 000 000 in that field. Spousal credit will not be calculated in this instance.
You can file an uncoupled return but you still have to check that you are married.
When it says "Lets get started" and asks who you are preparing the return for select "My spouse/partner and me". And then on the "How do you want to prepare your return" select "No, I want to prepare my return separately from my spouse/partner" because you want to file separately from your spouse