Input tax credit (ITC)

When a registered business buys something for the business, the GST on that purchase is not a cost: it can be subtracted from the GST collected on its own sales, and only the difference is paid to the government. That subtraction is input tax credit.

The credit only exists if your supplier is registered, puts your GSTIN on the invoice and reports the sale in their own return, so it shows up on your side. Choosing a supplier who does that properly is worth money. Businesses on the composition scheme cannot claim it.