A schedule C filer is usually on a cash basis. So when you said accrued, what do you mean? Whatever filing he did of his schedule C in 2018 would have to be on a cash basis. Therefore, any expenses that happened in 2019 can be reported in 2019 as long as they were paid in that year. If the business received no income for 2019, then zero income should be reported.
So, on the whole your mother has the choice to file as either married filing joint (MFJ) or filing as a Widow. The one that gives her the biggest benefit should be used.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
