With a Single Member LLC, can franchise fees be fully written off in one year if that part of the business was sold?

[Carl]

You need to provide more details. Don't know what you mean by "that part" of the business. In general, either you sold the entire business, or you did not.

If you sold the entire business "AFTER" you paid the franchise fee, then the fee is a deductible business expense as it was in past years when you paid the fee.

[MinhT1]

Your single member LLC is a disregarded entity for tax purposes. You can report its income and expenses on your schedule C.

If the part of your business was sold during the year, the unamortized portion of the franchise fee can be written off as an expense in the year of sale.