7 common invoice mistakes and how to avoid them

A mistake on an invoice can mean waiting longer for payment, so check your invoices carefully before sending them to your customers. Incorrect or incomplete information make an invoice invalid, and then the customer doesn’t have to pay it. Here we list the seven most serious mistakes companies make so you can be sure that you are preparing correct invoices!

common invoice mistakes and how to avoid them


Mistake 1: your invoice is unrecognisable

Put your logo and/or name clearly on the invoice, so your customer immediately knows it is from you. Preferably use a fixed template that is always recognisable by your customer. It is also crucial that you include the word “Invoice”.


Mistake 2: your invoice is missing important dates

Two dates should be mentioned on a perfect invoice, one, the date it was sent and two, the due date. The sent date is the date you send the invoice to your customer. The due date is the ultimate payment date of the invoice.

This due date depends on the payment term you have specified in your general terms and conditions. The maximum is 60 days. If you don’t have general terms and conditions, the due date is automatically 30 days after the sent date.


Mistake 3: incorrect or incomplete information

On every invoice, you must state both your full details and the customer’s full details. By this, the legislator means:

  • the official trade name (the name linked to the company number, which may differ from the commercial name)
  • the full physical address
  • the VAT or company number

Do not forget to mention your IBAN number. This way, your customer will not have to look up your account number and will be able to pay your invoice more quickly. In other words, make it as easy as possible for your customer to pay.

Also, make sure you provide a clear description of the services or products you have delivered. This will help avoid discussions about the content of the invoice.


Mistake 4: incorrect or missing invoice number

A unique invoice number required by law is to be stated on every invoice. These numbers should follow each other so the tax authorities can check your accounts properly for many reasons, including unpaid invoices. For example, 2022001, 2022002, etc.


Mistake 5: the amounts on your invoice are unclear

Your customer should know at first glance how much they must pay and which components the amount comprises. Ideally, you should state the unit price, the number of units, the total price without VAT, the VAT rate applied, and finally, the total amount, including VAT.

It is vital that you state the correct VAT rate. Depending on the service or product you provide, it will be 6%, 12%, or 21%. Keep it clear for your customer and split your invoice amounts according to the relevant VAT rate.

Avoid putting costs on your invoice that were not initially agreed or mentioned in the quotation. In this way, you minimise the risk of non-payment.


Mistake 6: the language is wrong

You should draw up your invoices in the language of the country or region where you are based. Is your invoice in a different language? That’s not a problem if your customer pays. If your customer does not pay, you could have an issue.

How do you prevent this with a customer who does not understand your language? To avoid misunderstandings, you may add an exact translation to your invoice.


Mistake 7: your invoice has been changed

Once you have sent your invoice to your customer, you are not allowed, by law, to change it. Adding or deleting something is prohibited.

If you invoice too much, you can solve this with a credit note. If you invoice too little, you must issue an additional invoice.


Finally, we would like to clear up one more misunderstanding; an RLE listing for your customer is not compulsory, even though some sources say it is. Therefore, you do not need to refer to the Register of Legal Entities (RLE) of the municipality in which your customer has its registered office.

If you avoid these common mistakes, you will automatically prepare correct invoices. To make it even easier for you, we have prepared a sample invoice.

Download a sample invoice


Do you currently have unpaid invoices, and are you tired of wasting your time on them?

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Would you like some more information? Feel free to call us on +32 9/396.34.00 or mail us at info@unpaid.be.