To enable sizes on any product:

1. Open Products and edit the item (or click Add Product).
2. Under Selling options, switch on Size Variants.
3. In the variants table that appears, click the Add Size button to create rows for each size (e.g., S, M, L, XL or 7, 8, 9, 10).
4. Enter the size label in the first column.

In the size variants table, every size has its own independent settings:

• Size: The label displayed on bills (e.g. M, 38, or UK 9).
• Variant SKU: An optional unique SKU code for this specific size.
• Barcode: Scan or enter a distinct barcode for this size so scanning immediately identifies the exact size.
• MRP (Max Retail Price): Maximum retail price printed on that size's packaging.
• Sale Price: Your actual selling price for this size.
• Buying Discount % (from MRP) or Buying Price: Your purchase cost for this size.
• Opening Stock: How many pieces of this specific size you have in the shop today.
• Low Stock Alert Threshold: Set a minimum alert quantity (e.g., alert me when size L drops below 2 pieces).

Click Save Product when done.

When you sell a sized item on the invoice screen:

1. Searching or scanning the product opens the Choose Size popup displaying all available sizes, their prices, and remaining stock.
2. Tap the size requested by the customer.
3. On the bill row, the selected size appears as Size: M. If the customer changes their mind, click Switch Size to swap the size without deleting the row.
4. When using Quick Select, you can tap Add another size to quickly add multiple sizes of the same shirt or shoe to the bill.

• On thermal paper rolls, A4 invoices, and shared WhatsApp PDF links, the size is clearly appended to the product title as Product Name size - M (for example, Men Polo T-Shirt size - XL).
• The rate, discount, and GST calculate based entirely on the chosen size's pricing rules.

• Opening stock locks after save: Opening stock can only be entered when creating a new size. After saving, any stock changes must be recorded through Purchase Bills or customer returns.
• Sizes with history cannot be deleted: If a size has ever been billed, bought, or stocked, it cannot be permanently deleted. You can archive it so it no longer appears for new sales while preserving past accounting history.
• Cannot combine with loose sales: Products cannot have both loose sales and size variants enabled simultaneously.
• One-way setup: Once sizes have recorded sales history, turning off variants on that product is locked to protect your sales reports.