You can choose to record a stock check at the same time as making an entry in your CD register. On the supply, book stock and correction pages you'll see a checkbox to confirm that you've counted the remaining stock:

You will also see when the drug was last counted, either through the method described here or as part of a full stock check.

If you click the checkbox, it will expand to show you the balance that should be in stock after the current operation. I.e., if you're making a supply entry, it will show you the balance remaining after the amount supplied has been subtracted:

Note: You need to enter a quantity before Clara can figure out what stock will remain

Entries made in the register with this box checked will show the balance in green, with a checkmark next to it, so you can see at a glance which entries included a stock check:

At the top right of the page for a specific drug, you'll also see some text telling you when you last checked the stock:

This will update each time you make an entry with the stock check box ticked, or perform a full stock check. Clicking on this text will take you to the last checked entry.

You can even enable stock check reminders either for all drugs or for specific drugs, and you will be reminded to do a check if it is overdue.