Why you need a checklist for OSS
The OSS return is quarterly and must be filed by the 30th day of the month following the end of the quarter. Even though it looks like “just one return” on paper, in practice it requires:
- consistent data from multiple marketplaces and stores;
- correct currency conversions;
- precise separation by country and rate.
An operational checklist lets you standardise the work and reduce dependence on one person’s memory.
Before the quarter: preparation
Before reaching the end of the quarter, it’s useful to:
- check that your OSS registration is active and that the data with the tax authority is correct;
- agree with your accountant on who does what (export, checks, filing the return);
- check that all marketplace → VATManager integrations are working.
This preventive stage avoids surprises close to the deadline.
Checklist stage 1: gathering files
For the quarter that just ended:
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Define the range:
- Q1: 1/1–31/3
- Q2: 1/4–30/6
- Q3: 1/7–30/9
- Q4: 1/10–31/12.
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For each channel (Amazon, eBay, Shopify, others) download:
- the complete sales reports for the period;
- the refunds/returns reports;
- VAT-specific reports (e.g. the VAT Transaction Report for Amazon).
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Check that no intermediate month is missing.
Checklist stage 2: import and normalisation in VATManager
Once you’ve gathered the files:
- import all the reports into VATManager;
- check that the system correctly recognises the columns (country, taxable amount, VAT, currency);
- check there are no structural errors (corrupted files, missing columns).
VATManager normalises:
- countries into ISO codes;
- currencies (with conversion to EUR for OSS where needed);
- transaction types (SALE, REFUND, transfers, etc.).
Checklist stage 3: checking time coverage
At this point:
- compare the number of days covered by the reports with the quarter’s 90/91 days;
- make sure every month of the quarter has reports for every active channel;
- check there’s no overlap (e.g. the same period imported twice with different files).
Many OSS errors simply come from time gaps or duplication.
Checklist stage 4: tax classification
VATManager classifies transactions into:
- domestic sales (outside OSS);
- intra-EU cross-border B2C sales (inside OSS);
- B2B sales;
- non-EU sales;
- any IOSS flows.
The checklist here is:
- check that your main selling countries are classified as you expect;
- review a sample of transactions per country to confirm the rate applied is consistent;
- make sure B2B sales don’t end up in OSS.
Checklist stage 5: aggregation by country and rate
To fill in the OSS return, for each country of consumption you need:
- the total taxable amount by rate;
- the total VAT by rate;
- the currency (usually EUR).
VATManager generates this table automatically. Before using it:
- compare the totals with your accounting data (at least at an order-of-magnitude level);
- check there are no anomalous values (e.g. countries with unexpectedly high or low volumes compared to the previous quarter).
Checklist stage 6: final checks and anomaly detection
Before passing the data to your accountant or uploading it to the OSS portal:
- use any anomaly detection features to spot outliers (countries that disappeared, unusual rates, unexplained negative amounts);
- check that any credit notes have been counted in the correct quarter;
- check that the exchange rates used are the expected ones (e.g. ECB for the relevant period).
These checks reduce the likelihood of problems surfacing after filing.
Checklist stage 7: handover to the accountant and archiving
Finally:
- export the OSS report by country × rate × period from VATManager;
- send the file to your accountant together with a short note (which channels are included, which rules were applied);
- archive both the marketplace source files and the consolidated reports, so you can produce them in case of an audit for at least 10 years.
A checklist like this, repeated quarter after quarter, turns OSS into a manageable, predictable process, instead of a “last-week nightmare” every three months.