Overview

On March 1 2026 Helium 10 released a detailed guide that outlines the accounting and tax obligations for Amazon and other marketplace sellers. The publication highlights the legal steps required to stay compliant and shows how organized bookkeeping can prevent fines, account suspensions, and loss of market edge.

Key Points

• Mandatory tax registration — Most jurisdictions require any online retailer generating revenue to enroll with the tax authority before opening a storefront; for instance, Spain demands filing the 036 form prior to sales.
• Sales‑tax collection — Sellers must add the appropriate VAT or GST based on the buyer’s location, such as applying a 21 % VAT rate to a purchase shipped to Madrid, while a sale to Barcelona may qualify for the reduced 10 % rate on essential goods.
• Periodic filing duties — Tax agencies expect quarterly returns (e.g., Spain’s model 303) and an annual summary (model 390), which means gathering all purchase and sales invoices for each reporting period.
• Electronic bookkeeping mandate — Since 2024 the Spanish Tax Agency requires the real‑time transmission of invoice registers through the SII, forcing merchants to adopt software capable of producing compliant XML files.
• Platform commissions and withholdings — Marketplaces like Amazon deduct a fixed percentage from each transaction—15 % is typical for electronics—and provide an annual statement that must be incorporated into the seller’s income declaration.
• Allowable expense deductions — Costs such as shipping, FBA storage, Amazon advertising, and subscription‑based management tools can be written off, provided they are backed by valid invoices, thereby lowering the taxable profit base.

How the Accounting and Tax Process Works for Ecommerce

1. Business registration and classification — The seller establishes a legal entity (sole proprietor, limited company, LLC) and records it with the local economic activity registry; for example, Ana, who sells fashion accessories from Barcelona, registers as a self‑employed professional under activity code 659.9.