I do not have my last name on SIN and here last name is required. So what can I do now?

TurboTax team strongly recommends you contact CRA and ask them this question as if you put in the last name field "Not Applicable" you might not be able to proceed with NetFile. 

Entering anything in the last name field will allow you to continue with preparing the return, but when it comes time to NetFile you will most likely get rejected.

To contact CRA,

• call 1-800-959-8281 or 
• follow this link Individual tax inquiries line. 

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