Generate a Spreadsheet Formula to Flag Overdue Invoices

The invoice tracker has forty rows and you are eyeballing due dates one at a time, which is exactly the kind of task a formula should be doing instead. This writes one that labels each row OVERDUE or OK, skips blank rows cleanly, and comes with a one-line explanation so you can change the day threshold yourself.

Write a spreadsheet formula (specify whether it is for Excel or Google Sheets) that flags an invoice as overdue when today's date is more than [30] days past the date in the due date column. The formula should return a clear text label such as OVERDUE or OK rather than TRUE or FALSE, and should not error on blank rows.

Explain in one sentence what each part of the formula does, so I can adjust the day threshold myself later.