Yes! ShipStation allows you the most flexibility possible in regards to your subscription plan. If your needs increase or vary by season, you can change your billing plan to fit your needs.
Head to your Account Settings (the wrench icon in the upper right).
Next, select Account Settings and then Subscription from the sidebar on the left.
From here, find the Current Subscription section and click Change Your Subscription.
If you're upgrading
You can upgrade your plan at any time, and changes take effect immediately. Please note that the current month’s charges will be pro-rated based on the date of upgrade.
If you're downgrading
You can downgrade your plan at any time. Since subscription periods are billed in advance, please note that the current month will continue to the end of the period at the plan level it began, with the new plan taking effect on the following billing cycle. So, if you upgrade for the remainder of a month, once that is applied to your account, you can immediately downgrade and that downgrade won't take effect until the start of the new billing cycle.