Accurate data is essential for preparing and filing VAT Returns, EC Sales Lists (EC Reports), and OSS Quarterly Returns. Small mistakes can create filing delays, tax office questions, incorrect VAT declarations, or compliance risks.

This article lists the most common errors and misunderstandings we see — and how you can avoid them.

1️⃣ Incorrect or Incomplete Transaction Data

✔️ Missing Marketplace or Webshop Data

Many clients assume integrations “automatically” include everything, but missing API permissions, failed syncs, or new sales channels often lead to gaps.

Common issues:

• A new marketplace not yet connected

• Partial data sync (e.g., missing refunds or returns)

• Manual orders not uploaded

• Only exporting sales without including shipping or handling fees

Impact: Missing data = incorrect VAT, EC, or OSS reports.

✔️ Mixing Domestic and Cross-Border Sales

A frequent misunderstanding is not knowing which sales belong in which filing.

For example:

• German → German sales belong in the domestic VAT return

• Germany → EU B2B with VAT ID belongs in EC listing

• Germany → EU B2C belongs in OSS (if registered)

Mixing these leads to misreported VAT and tax office corrections.

✔️ Incorrect VAT Rates

Many sellers assume their platform applied the correct VAT rate, but mistakes happen:

• Wrong VAT rate for reduced or special categories

• Using domestic VAT instead of destination-country VAT in OSS

• Applying B2B VAT rules to B2C customers (or vice versa)

The tax office may request amendments or issue penalties.

2️⃣ Wrong Customer Classification (B2B vs B2C)

A very common problem is misunderstanding which transactions count as:

• B2C (Consumer) – must go into OSS or domestic VAT return

• B2B (Business) – often zero-rated and reported in EC Sales List

Typical errors:

• Treating every sale with a VAT number as B2B (some VAT numbers are invalid or not verified)

• Assuming marketplaces always classify customers correctly

• Using VAT rates incorrectly when customer information is incomplete

Always validate VAT numbers when applying the reverse-charge mechanism.

3️⃣ Confusion About Returns, Refunds, and Cancellations

These adjustments must be included in the same period they occurred, not the period of the original sale.

Common misconceptions:

• “Refunds don’t need to be reported.”

• “Returns are automatically handled by the marketplace.”

• “Cancellations shouldn’t affect VAT reports.”

Incorrect handling of adjustments leads to VAT mismatches.

4️⃣ Inaccurate Country-of-Destination for OSS Reports

OSS requires you to declare VAT based on the customer’s country, but errors occur when:

• Orders are assigned the wrong shipping country

• Fulfilment centres cause confusion (e.g., DE → DE warehouse → FR customer)

• Sellers use origin-country VAT instead of destination VAT

This is one of the most common OSS compliance issues.

5️⃣ Missing or Incorrect B2B Data for EC Sales Lists

EC Sales Lists require:

• Valid VAT ID

• Matching customer details

• Correct reporting period

Frequent mistakes:

• Invalid VAT IDs used without verification

• Adding B2C transactions by accident

• Reporting the wrong total (e.g., tax-inclusive instead of net value)

The tax office may reject the EC return if this data is incorrect.

6️⃣ Uploading Data Late or Outside the hellotax System

Misconception:

“I emailed my data, so it counts as submitted.”

Emails cannot be used for filing.
All VAT, EC, and OSS data must be uploaded through your hellotax account.

Consequences:

• Late-data fee (€119)

• Manual processing required

• Filing delays and potential tax office penalties

Uploading before the 4th day of the following month is essential.

7️⃣ Including Non-EU or Non-Reportable Transactions

Examples of unnecessary or incorrect inclusions:

• UK or Swiss transactions included in EU reports

• Shipping-only items reported as revenue

• Internal stock movements included as sales

• Transfers between warehouses reported as transactions

These cause inconsistencies and audit flags.

8️⃣ Incorrect Invoicing Assumptions

Common seller misconceptions:

• “Marketplaces handle VAT invoicing, so I don’t need to track it.”

• “If I issue no invoices, there is nothing to report.”

• “VAT reporting is based on bank payments.”

VAT reporting is based on transactions, not invoices or payouts.

🟦 Summary: Most Common Errors at a Glance

🛠️ How to Avoid These Errors

• Upload all data before the 4th

• Use marketplace/shop integrations whenever possible

• Validate customer VAT numbers for B2B

• Keep refunds/returns aligned with their actual date

• Review your OSS-required countries regularly

• Ensure all data is uploaded—not emailed