If you have changed your marital status during the tax year, you can start your return (self) and file separately, but you will have to enter the ex-spouse/ex-common-law partner's information and enter the separation date.
If you have been separated for more than a year, you file a separate tax return and you don't need to enter your ex's information.
If you have already started filing your return and your partner's return then decided to file a separate return, unfortunately, you will not be able to delete the partner's return or remove the information. You will need to start a new return to file a separate return.
I hope this was helpful
