Hello there, EdwardSam.

As my colleague MariaAlmaT mentioned above, you can still access your forms as well as running a report. Aside from not getting any updates about your QuickBooks file, running payroll is also not available once your subscription ends. 

On the other hand, yes you can extend your payroll subscription. I have here an article about the payroll subscription auto renewal period.

Feel free to post here again if you have other questions.