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Errors in an outgoing invoice happen faster than you think – and in the worst case, she can be costly. That's why it's especially important for founders and young companies to know what typical errors look like and how to correct them correctly.
Common errors in invoice
Outgoing invoices can contain errors in various areas, for example:
- simple calculation errors
- incorrect quantity information
- an incorrect invoice date
- an incorrect invoice number
- missing tax number or VAT ID number
- inaccurate or incorrect descriptions of goods or services
- missing date of service (time of delivery/service)
- an incorrect VAT rate
- incomplete or incorrect address information
What consequences incorrect invoice can have
Mistakes are not only annoying, but can also have tax consequences, especially in connection with value added tax.
If you declare, for example, an excessive amount of VAT, the tax office can demand that you pay exactly that amount – even if it wasn't actually owed. Furthermore, incorrect or incomplete invoices can give the impression of inadequate bookkeeping, which leads to closer scrutiny during audits, for example by the tax office.
Above all, incorrect invoices cause frustration for your customers.
If you have business customers: If an invoice doesn't contain all the required information or has factual errors, the tax office may not accept it. The VAT paid then cannot be claimed as input tax. Depending on the invoice amount, this can quickly cost several hundred or even thousands of euros.
With private customers, it's more about annoyance and an uneasy feeling. The frustration is therefore more emotional, but it can – even subconsciously – tarnish your positive image.
Another problem is delays and liquidity issues:
If customers reject incorrect invoices or insist on corrections, payment is delayed. And this can quickly lead to cash flow problems, especially with larger invoices.
And of course, correcting an incorrect invoice always involves effort, frustration (with yourself), and sometimes real stress.
It costs you time and effort to find errors, correct the invoice, and possibly resend or reconcile it. You're frustrated or annoyed because you made the mistake yourself. And there can be additional pressure – for example, if you have deadlines to meet, if customers (annoyed) ask questions, or if there are financial consequences.
Options for invoice correction
How an invoice is corrected depends on when the error is discovered:
- The invoice has not yet been sent.
If you spot the error early, you can simply correct it directly on the original invoice.
If you've already entered it into your system, you'll need a credit note and a new, correct invoice. The credit note contains the same items as the original invoice but shows the invoice amounts as negative values (or with a clear cancellation note) to reset the original revenue to zero.
Important:
- Clearly mark changes
- Add the date of the change
- Don't forget your signature
- After shipment to the customer or
If the incorrect invoice has already been received, you must create a separate correction document:
- as a cancellation invoice (retains all original documents)
- as a correction invoice (specifically corrects errors).
This document refers to the original invoice, identifies the error and its correction, and thus ensures complete documentation.
Both parties should retain this document along with the original invoice.
- Errors identified during a tax audit
Problems arise when errors are only discovered during a tax audit. If an invoice is then rejected, this can lead to the disallowance of input tax deduction. The consequence: Amounts already refunded must be repaid to the tax office. Interest may accrue on back payments, and in the worst-case scenario, fines or problems due to formal deficiencies
may occur. While some invoices can be corrected retroactively, this is only possible if they contain certain minimum information. You can find out more in our article: How to create a correct invoice.
If the minimum information is missing, the document is not considered a valid invoice for tax purposes. In that case, no retroactive correction is possible, and the input tax deduction is permanently lost.
Conclusion
Careful invoicing saves time, stress, and potentially money. Knowing and correcting common errors early on helps avoid problems with customers and the tax authorities. Especially during the startup phase, it pays to work meticulously from the beginning and double-check invoices.
By the way, the rules mentioned above also apply to e-invoices, which—apart from some exceptions and transitional provisions—have been mandatory since 2025 (see our article “E-invoices: Issuance mandatory from 2025”).
The only difference: Many errors are detected more quickly due to the automated processes involved in invoice creation, so the error rate for sent invoices is likely to be significantly lower!
