Set Maintain Batch-wise Details and Set Expiry Dates for Batches to Yes in the F11: Inventory Features screen.
Set Use different Actual & Billed Qty. to Yes in F11: Inventory Features screen to specify the free items.
Set Separate Discount column on Invoices to Yes to specify the discount on any items while making a POS sales invoice.
Create Stock Items. Place the cursor in the alias field and use the Bar Code Reader to scan and read the bar code of the Item. This code will automatically get displayed in the alias field. Select the Unit of measure and Set Maintain in Batches to Yes. On setting this option you will get Track Date of Mfg and Use expiry dates set these two fields to Yes.
Set Standard Rates to Yes and enter the standard selling price of the Item (Press F12: Configure button in the Stock Item creation screen and Set Allow Std. Rates for Stock Items to Yes). If you have specified the rates in the price level then you can skip this field.
Set Use Security Control to Yes in Company Creation/Alteration screen and create the user login name using the security feature in Tally.ERP 9. The user who logs in to Tally.ERP 9 with the name of the user and password can print the POS Invoice with the user name.
More :
Creating a POS Invoice using Voucher Class
Creating a POS Invoice with Batchwise Details
Creating a POS Invoice with different Actual & Billed Qty