How do I lock months to prevent changes?

You can lock any selection of months in any of your scenarios in Budgyt which prevents users from editing the data on the data sheet pages.  This is ideal for Actual data that has no need to be updated or if you want to lock down a Budget that is completed.

Go to Budgets > Manage Budgets, and click the Pencil Icon for the budget that you are working on, then simply select the months that you wish to lock, and hit Save. Now when you look at any category in the data sheet for that budget you will see a padlock next to the periods that are locked.