There are the steps for update invalid HSN code in BUSY:
Step 1: Go to Administration Menu
Step 2: Click on Bulk Updation Option
Step 3: Then click on Check/update item HSN/Tax Category
Step 4: Then, select the Item master range as ALL, GROUP-wise or Selected
Step 5:You can apply filters to HSN, name, and tax category by clicking on the filter option, and then proceed to update the HSN code.
Note : If a single item's HSN code appears as invalid in BUSY, it's advisable to verify it on the GST portal.