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The Best Way to Merge Amazon Seller Central and Mercari Data for Side Hustle Bookkeeping

If you're doing side hustle bookkeeping by hand right now, here's the fastest path from "two exports" to "one usable sheet," and why the manual version keeps breaking.

Step by step

  1. Decide your target columns once. Most people settle on Date, Channel, Order ID, and Total — set that up in CSV Experts and you won't redo it.
  2. Import the Amazon Seller Central file first. The first time you see this file shape, you map each of its columns to your target list.
  3. Import the Mercari file the same way. Its columns get mapped once too — after that, every future file with this shape merges with no extra clicks.
  4. Check the merged totals. Dates and numbers are normalized automatically, so a European "24,00" and a US "24.00" both land as the same value.
  5. Export. CSV or Excel, ready for side hustle bookkeeping.

What actually goes wrong if you do this by hand

Amazon Seller Central gives you a purchase date/time column stamped in UTC, not your local time, while Mercari gives you a sold date in the seller's local time — line those up manually across a few hundred rows and it's easy to miscount a week. On top of that, Amazon Seller Central's export reports differ noticeably between the 'All Orders' report and the Payments/Settlement report — totals rarely match at a glance, and Mercari's like other reseller apps, the export is minimal with no tax breakdown and mixes cancelled orders into the same file. Individually those are minor quirks; combined into one spreadsheet by hand, they're where most reconciliation errors for side hustle bookkeeping actually come from.

Why it matters for side hustle bookkeeping

Running sales channels as a side hustle usually means doing your own books, which gets tedious fast once more than one platform is involved.

Try it with your own files →

Just want the quick column-difference reference instead? See the short version.

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