docs: info on VAT ID Check limitations in README

README.md

@@ -18,6 +18,9 @@ App to hold regional code for Germany, built on top of ERPNext.
 
     ![Validate EU VAT ID](docs/vat_check.png)
 
+    > [!INFO]
+    > Currently, we always check four customers that didn't have a VAT ID Check in the last three months. If these four all have an invalid VAT ID, we get stuck.
+
 - Allow deletion of the most recent sales transaction only
 
     This ensures consecutive numbering of transactions. Applies to **Quotation**, **Sales Order**, **Sales Invoice**.