How to prepare your accountant for the OSS return: checklist and materials

The OSS return is often physically filed by your accountant, but the quality of the work largely depends on how you hand them the data. If they receive scattered files and numbers to interpret, that increases the time spent, the risk of errors and the likelihood of missing the deadline.

The deadlines you can’t miss

The OSS return has fixed deadlines, with no extensions:

The OSS VAT payment has the same deadline as the return. Hand over the data at least 10 days before the deadline to give your accountant the margin they need.

Complete checklist: what to hand over every quarter

Mandatory documents

• Aggregated OSS report by country — a table with country of consumption, rate, taxable amount, VAT due for every country/rate combination in the quarter
• List of included channels — confirmation of which marketplaces and platforms were included in the data (Amazon, eBay, Shopify…)
• Credit note treatment — confirmation of whether the period’s refunds were included in the aggregated report as negative values
• Confirmation of active scheme — are you on standard OSS or IOSS? Were there any changes during the quarter?

Documents recommended for traceability

• Original marketplace files — Amazon VAT Transaction Report, eBay reports, Shopify exports for the period
• Currency schedule — if you have sales in GBP, SEK, DKK: the conversion rate used and its source (ECB, period average rate)
• List of countries with local VAT — if you have FBA warehouses in other EU countries, confirm which countries are covered by a local VAT number and therefore excluded from OSS
• Any adjustments from previous quarters — if you corrected errors from past periods, document what you changed and why

Contextual information to attach once (or when it changes)

• OSS activation date and any scheme changes
• Updated list of countries with a local VAT number
• Agreement on which exchange rate to use for foreign currencies

How to structure the folder you hand over

A simple, repeatable structure every quarter:

OSS_2026_Q1/
├── 01_marketplace_input/
│   ├── amazon_vat_transaction_report_Q1_2026.csv
│   ├── ebay_vat_report_Q1_2026.xlsx
│   └── shopify_tax_report_Q1_2026.csv
├── 02_vatmanager_output/
│   ├── oss_summary_country_rate_Q1_2026.xlsx
│   └── oss_summary_Q1_2026.pdf
└── 03_notes_and_explanations/
    └── notes_Q1_2026.txt

Share the folder via Drive or Dropbox — don’t send scattered email attachments.

Template: cover note

The document in the 03_notes_and_explanations/ folder is often the most useful one for your accountant. Here’s a template:

OSS RETURN — Q1 2026
Prepared by: [name]
Date: [delivery date]

CHANNELS INCLUDED: Amazon EU, eBay, Shopify
CHANNELS EXCLUDED: none

SCHEME: standard OSS (active since 01/07/2021)
COUNTRIES WITH LOCAL VAT: DE (active FBA warehouse), PL (active FBA warehouse)
  → Sales with Germany stock as origin are excluded from OSS
    and handled separately under the DE VAT number

CURRENCY: GBP transactions converted to EUR at the Q1 2026 average ECB rate
  (rate used: 1 GBP = 1.1742 EUR)

SPECIAL NOTES:
- There was a spike in returns on Amazon.de in March: included as negative REFUNDs
- No adjustments to previous quarters

ATTACHED FILES:
- [file list]

4 common mistakes that slow your accountant down

1. Handing over the raw VAT Transaction Report without aggregation Your accountant shouldn’t have to filter thousands of CSV rows. Their input should be the table aggregated by country/rate, not Amazon’s raw dump.

2. Not stating which countries have local VAT If you have FBA warehouses in Germany or Poland, sales with stock from that country don’t go into OSS. If you don’t specify this, your accountant might include them by mistake, leading to a double declaration.

3. Forgetting secondary channels Many sellers remember Amazon but forget eBay or their own Shopify store. If a channel isn’t included, the VAT on those sales doesn’t get declared.

4. Handing over the data 2-3 days before the deadline If questions or discrepancies come up, there’s no room to fix them. The risk is filing the return with unverified data or missing the deadline.

📎 Learn more: Quarterly OSS export — an operational checklist — How to read a per-country VAT report — Annual VAT return for e-commerce sellers — Data retention and GDPR for tax reports

Frequently asked questions

By when do I need to hand the data to my accountant? The OSS return must be filed within 30 days of the end of the quarter. Hand over the data at least 10 days before the deadline: by 20 April for Q1, 20 July for Q2, 20 October for Q3, 20 January for Q4.

What happens if the OSS return is filed late? A late return leads to penalties and late-payment interest. In case of repeated omission, exclusion from the OSS scheme is possible. It can be regularised through voluntary disclosure, but it’s much better not to get there.

Do I also need to hand over the original files, or is the aggregated report enough? The bare minimum is the report aggregated by country/rate. The original files (Amazon VAT Transaction Report, Shopify reports, etc.) are recommended as a backup for traceability in case of an audit.