GST Invoices for Your Store

Mercayo issues a GST-correct document for every order by itself, in your own gapless series, and a credit note for every cancellation, undelivered COD parcel and refund. This guide sets it up end to end and explains what to give your accountant each month. General guidance, not tax advice: your CA decides what applies to your business.

Step 1: Tell Mercayo Your Registration

Open Settings › Taxes and choose your Registration Type:

Mercayo checks the GSTIN's shape, its check character and that its state code matches your state. Then choose Your Prices and GST: whether the prices you type include GST. See Taxes.

Step 2: Give Every Product an HSN Code and Rate

1. In Settings › Taxes › GST Rates by HSN Code, press ADD RATE, search with Find an HSN Code, and USE CODE AND RATE for each kind of product you sell (for example 4202 for cases, 7117 for imitation jewellery).
2. In each product's GST card, type or pick its HSN Code. The card tells you whether your store charges a rate for it ("Your store charges 18% for this code, the same as the list.") and offers to add one if not.

On regular GST, a product cannot be bought without an HSN code and a rate for it. When the law changes a rate from a date, add the new rate with Applies From; orders already placed keep theirs.

Step 3: Choose When Invoices Are Issued

In Settings › Invoices:

• Issue the GST Invoice when the order is confirmed (default: a COD order when placed, an online order when paid), or when it is shipped. An order that ships without one gets it then.
• GST on Delivery and Fees (18% by default): the rate on delivery charges and COD fees, which appear on the invoice with their GST.
• Your number prefixes: INV/ for invoices, CN/ for credit notes, BOS/ for bills of supply by default. Numbers read INV/2627/00001 (financial year 2026-27), run without gaps, and restart on 1 April.

Every one of these is explained in Invoice Settings.

How GST Is Split

The place of supply is where the order is delivered:

• Delivered within your state: CGST and SGST, half the rate each.
• Delivered to another state: IGST at the full rate.

A business shopper can give their GSTIN and business name at checkout (GST Invoice for Businesses, on by default); the invoice then names the business so they can claim input tax credit. Their GSTIN must belong to the delivery state.

Credit Notes

Issued automatically, once per event, against the original invoice:

• an invoiced order is cancelled;
• a COD parcel is returned undelivered;
• a refund is made from the order (to the original payment, as store credit, or recorded by hand).

Downloading

• One order: the order page's GST Invoice card, DOWNLOAD, and each credit note.
• Many orders: on the Orders list, select them and DOWNLOAD INVOICES (one PDF, or a ZIP of PDFs, up to 100 orders at a time).
• Shoppers download their own invoice from their order page.

Each Month, for Your CA

1. Orders › Invoices: press EXPORT FOR GSTR-1, choose Last Month (or Last Quarter if you file quarterly) and give the ZIP to your CA. See Invoices and the GSTR-1 Export.
2. Analytics › Reports: GST by Rate and HSN Summary for the month, to check the totals.

Good to Know

• Issued invoices and credit notes are frozen: changing a product, a rate or your details later never changes them.
• E-invoicing (IRN and QR code), required above a turnover threshold, is not built.
• An invoice never stops a sale: if one cannot be issued, the order goes ahead, its timeline says why, and ISSUE INVOICE tries again.

Questions

I am not registered yet. Can I sell?

Yes. Choose Not registered for GST: you charge no GST and issue no tax invoice. Change it when you register.

Can I issue an invoice for an old order?

Press ISSUE INVOICE on a confirmed, shipped, delivered or closed order that has none. An order that charged no GST is never taxed after the fact.

Are prices with GST or without on the invoice?

The invoice shows taxable value and GST separately, with the total, and says "Prices include GST" when they do.