How to issue an invoice in the age of mandatory e-invoicing?
A complete guide for freelancers and small businesses
Follow our step-by-step guide through the entire invoicing process and find out how to handle the transition to mandatory e-invoicing without stress, data retyping, or expensive software.
How to issue an invoice in the age of mandatory e-invoicing?
A complete guide for freelancers and small businesses
Follow our step-by-step guide through the entire invoicing process and find out how to handle the transition to mandatory e-invoicing without stress, data retyping, or expensive software.
Date: 10.7.2026
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Posted by: Judita Joštiaková
How to issue an invoice in the era of mandatory e-invoicing?
An invoice is not rocket science. If you issue only a few invoices per month, you can manage it even in Excel, Word or an old template that you keep copying over and over.
But then things start falling apart.
Incorrectly entered data. Forgotten due dates. An invoice saved in the wrong folder. A client claims they never received it. You do not know whether they paid. Your accountant asks for documents and you search through PDFs in your emails.
On top of that, mandatory e-invoicing is approaching and another question arises: "Will my current invoicing method be sufficient after the legislative changes?"
You do not have to change your entire system immediately or deal with an expensive IT project. Sometimes it is enough to finally have your invoicing in one place.
QASIDA Invoice Manager is a simple cloud application for freelancers and small businesses. Starting from just €5 per month, you can conveniently issue invoices, send them by email or via Peppol, track payments and keep your documents organised.
Let us show you how to issue an invoice correctly even at a time when invoicing is gradually moving into a digital format.
Replace manual and unclear invoicing with simple and organised document processing in QASIDA Invoice Manager.
What must an invoice contain?
An invoice is a document through which a business charges a customer for delivered goods or services. To be correct, it must contain basic information about the supplier, customer, invoiced goods or services, price and payment.
The exact scope of required information also depends on whether you are a VAT payer or non-VAT payer. In practice, however, you should always check the following details on every invoice:
- supplier details,
- customer details,
- invoice number,
- issue date,
- delivery date, if required,
- due date,
- description of the service or goods,
- quantity and price,
- VAT rate and VAT amount, if you are a VAT payer,
- total amount payable,
- payment method,
- bank account.
With manual invoicing, many things can be accidentally changed. It is enough to forget to update the invoice number, date, customer details or amount. And that is exactly when simple administration becomes a problem that unnecessarily takes away your time.
How to issue an invoice step by step?
Issuing an invoice does not have to be complicated. The important thing is to have correct information, clearly stated items and a reliable way of sending the document to the customer.
1
Select or add a customer
First, add the customer's details. For a company, this mainly includes the company name, address, company ID, tax ID and VAT ID, if available.
If you invoice frequently, manually entering data slows you down unnecessarily and increases the risk of errors. It is an advantage if an invoicing program can automatically complete company details.
QASIDA Invoice Manager uses the Firmsio register for Slovak and Czech companies. Simply enter the company name or company ID and company details are automatically filled in. You save time and reduce the risk of typing errors.
2
Add invoice items
Complete what you are invoicing. It can be a service, product, rental, service intervention or another delivery. For each item, specify the quantity, price and, if applicable, VAT.
A good invoicing program helps you with preset information, numbering, dates and due dates. Thanks to this, you do not have to start from scratch with every invoice.
3
Check amounts, dates and due date
Before sending the invoice, check especially the total amount, VAT, issue date, due date and bank account.
If the customer pays by bank transfer, it is practical to add a QR code for payment. QASIDA Invoice Manager supports QR payments via Pay by Square. The customer scans the QR code in mobile banking and completes the payment more easily.
4
Send the invoice to the customer
Today, you can send an invoice for example by email. However, in the era of mandatory e-invoicing, sending invoices via Peppol will also be important for selected transactions.
QASIDA Invoice Manager allows you to send invoices by email or via Peppol. You can therefore handle regular invoicing today while also having a prepared method for sending electronic invoices when you need it.
What changes with mandatory e-invoicing?
The biggest change is that an invoice should no longer be only a document that a person opens and reads. E-invoicing is about a structured electronic document that can be processed by software.
This means that invoice data does not have to be entered manually. The system can work with supplier, customer, amounts, VAT and other information automatically.
It is also important to understand that a PDF sent by email is not automatically an e-invoice. A PDF is mainly a visual document. An e-invoice is a data document in a standardised XML format.
In practice, it is therefore not enough to have a nice invoice template. You need a solution that can create and send an invoice in the correct electronic format.
Good news:
You do not have to deal with technical details yourself. You do not need to know what XML is, how the Peppol network works, through which XML invoices, meaning e-invoices, are sent, or in which format an e-invoice is created. If you use the right invoicing tool, the software takes care of the technical side.
Simply put:
A PDF invoice is a document for reading. An e-invoice is a data document that can be processed by software.
Is a PDF invoice sufficient?
For regular invoicing, a PDF can still be practical. The customer can open it, save it or send it to an accountant. The problem is that a PDF itself does not meet the requirements for an electronic invoice in a structured XML format.
Therefore, it is good to distinguish between:
- PDF invoice is a document suitable for reading, printing or sending by email.
- E-invoice is a structured electronic document in XML format that can be processed by software.
- An invoicing program ready for e-invoices such as QASIDA Invoice Manager can create both a regular invoice and an electronic invoice and send it in the correct way.
Do you currently issue invoices in Excel or Word? It may work when you have only a small number of documents. In the future, however, you will need certainty that you can create invoices in electronic format as well.
Does a freelancer have to issue e-invoices?
Not every freelancer will have to issue e-invoices from 1 January 2027. The key factor will mainly be whether they are a VAT payer and who they invoice.
If a freelancer is a VAT payer and issues invoices to other companies or entrepreneurs in Slovakia, they should prepare for mandatory electronic invoicing in time.
If a freelancer is not a VAT payer, the obligation to issue e-invoices generally may not apply to them in the first phase. However, this does not mean that e-invoicing will not affect them at all. They will certainly need to be able to receive electronic invoices from suppliers who will be required to send them via Peppol.
Therefore, it is sensible to use an invoicing solution that can handle not only regular invoices but also electronic invoices when needed.
Who will e-invoicing apply to from 1 January 2027?
In the first phase, mandatory e-invoicing in Slovakia is expected to apply mainly to VAT payers for domestic transactions. Simply put, this concerns situations where a Slovak VAT payer invoices another Slovak business entity.
Three questions you should ask yourself
Am I a VAT payer?
If yes, e-invoicing will be mandatory for you from 1 January 2027.
Do I invoice companies or entrepreneurs in Slovakia?
If yes, you should check whether your invoicing system supports e-invoices.
Can I also receive e-invoices?
It is not enough to think only about issued invoices. You should also prepare for receiving invoices from suppliers.
What if I invoice both companies and private individuals?
Many small businesses do not invoice in only one direction. Sometimes they issue an invoice to a company, other times to an individual. Sometimes the customer is a VAT payer, sometimes not. That is why it is important that an invoicing program supports both B2B and B2C invoicing.
QASIDA Invoice Manager supports invoicing for both companies and private individuals. In one application, you can manage invoices for business partners as well as customers – private individuals.
For invoices issued to private individuals, you can also use QR payments via Pay by Square. Customers simply scan the QR code in their mobile banking app and complete the payment more easily.
Why deal with e-invoicing today if it is not mandatory for me yet?
Invoicing is directly connected with money. If your system does not work properly, it can slow down invoice creation, receiving payments and processing documents.
If you prepare in advance, you will have more time to test a new invoicing process, reduce stress before the deadline, keep customer data organised, simplify receiving invoices from suppliers, get a better overview of issued and paid invoices and reduce manual data entry.
E-invoicing does not have to be only a legislative obligation. With the right solution, it can also be an opportunity to simplify your invoicing process.
The sooner you try the new invoicing process, the less stress you will have to deal with when the new legislation comes into force.
What if your current system does not support e-invoices?
You do not need to replace your entire system. If you currently use a simple invoicing tool, Excel or a solution that does not support Peppol, you can choose an application that helps you meet the new requirements without a major IT project.
QASIDA Invoice Manager is a cloud application that works through a web browser. You do not need your own server, hardware or local installation. All you need is an internet connection and you can work from the office, home or while travelling.
In one solution, you can issue invoices to companies and private individuals, work as a VAT payer or non-VAT payer, send invoices by e-mail or via Peppol and receive invoices from suppliers.
QASIDA Invoice Manager: invoicing ready for e-invoices
QASIDA Invoice Manager is designed for freelancers and small businesses. It helps with everyday invoicing while also providing built-in support for electronic invoices via Peppol.
✔ Invoicing without Excel
Create invoices in a clear application instead of spreadsheets and folders.
✔ Peppol sending and receiving
You can send and receive electronic invoices whenever you need them.
✔ Payment overview
See paid invoices, pending payments and payment history.
✔ Cloud without installation
All you need is an internet connection and a web browser. Work from the office, home or while travelling.
Frequently asked questions from freelancers and small businesses
Do I have to issue e-invoices as a freelancer from 1 January 2027?
Not automatically. It mainly depends on whether you are a VAT payer and who you invoice. If you are a VAT payer and invoice other companies or entrepreneurs in Slovakia, you should prepare for e-invoices.
Do I need to deal with e-invoicing if I am not a VAT payer?
The obligation to issue e-invoices generally may not apply to non-VAT payers in the first phase. However, even non-VAT payers will need to receive electronic invoices from suppliers.
Is a PDF invoice an e-invoice?
No. A PDF is a document intended for reading. An e-invoice is a structured electronic document in XML format. It may not be readable at first glance, but software can process it.
Do I need a new large ERP system because of e-invoicing?
Not always. If you are a freelancer or a small business, a simple cloud application supporting regular invoicing and e-invoices via the Peppol network, such as QASIDA Invoice Manager, may be enough.
Can I invoice affordably even in the era of mandatory e-invoicing?
Yes. QASIDA Invoice Manager costs only €5 per month and allows you to issue invoices, track payments, send documents by e-mail or via Peppol and receive invoices from suppliers.
Can I invoice both companies and private individuals?
Yes. QASIDA Invoice Manager supports both B2B and B2C invoicing. In one application, you can issue invoices to business partners as well as private individuals.
Do I need my own server to use it?
No. QASIDA Invoice Manager works in the cloud. All you need is an internet connection and a web browser.
Invoice easily today and be ready for the future
Mandatory e-invoicing does not mean that every freelancer has to change the way they run their business. However, if your suppliers start sending invoices through the Peppol network, you should be able to receive and process them easily.
If you currently issue invoices manually, in Excel or use a solution that does not support electronic invoices, now is the right time to switch to a modern invoicing tool.
You do not need to study new technologies or invest in a complex system. All you need is a solution that simplifies your everyday invoicing while allowing you to receive and send e-invoices through the Peppol network.
QASIDA Invoice Manager helps you invoice simply, securely and in line with new requirements. Without a server, without installation and without a large investment.
FROM €5 PER MONTH
Get an invoicing tool ready for the era of mandatory e-invoicing.