The short answer: Yes, but it will forfeit your days remaining discount (if you are owed one).
The longer answer: When renewing or upgrading your plan, as standard you will be offered a discount based upon the number of days you have remaining in your active subscription (if any). You can choose to use either this discount or the discount you can generate using a promotional code. You cannot apply a promotional discount on top of a days remaining discount.
The choice of which discount to use is yours!
Please note: Your renewal date will be reset to the latest payment date, and protection will last for a year from this new date.