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Merge Shopify and Walmart Marketplace Sales Data for Tax Prep in the United Kingdom

At tax time you need total revenue by channel without hand-fixing each export's columns first. In the United Kingdom, that also means accounting for VAT: VAT is charged at a flat 20% standard rate once you're registered, and HMRC expects consistent digital records under Making Tax Digital.

Why Shopify and Walmart Marketplace exports don't line up

Shopify: a Created At timestamp that includes a timezone offset; a single Total column that already nets out discounts, with tax broken out separately; an order Name like #1001 rather than a numeric ID.
Walmart Marketplace: an Order Date column separate from the ship-by date; item price and a separate Walmart referral fee; a numeric Purchase Order ID.

Neither export is built with VAT in mind, so getting from "two raw files" to "the United Kingdom-ready numbers" means normalizing dates/totals first, then applying your own VAT treatment on top of the merged total — not per platform separately.

How to merge them

Set your target columns once in CSV Experts (Date, Channel, Order ID, Total, and a Currency column if you sell in more than GBP).
Map the Shopify export, then the Walmart Marketplace export — each file shape is remembered after the first time.
Export the merged sheet and apply your VAT treatment to the combined total.

Merge your files now →

FAQ

Does this upload my sales data anywhere?

No. Everything runs in your browser using JavaScript — your files are never sent to a server.

Does it work for more than two channels?

Yes. Add as many source files as you want; each distinct file layout is mapped once and remembered.

Other countries for Shopify + Walmart Marketplace

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