How to issue FEL electronic invoices from your point of sale

If you sell in Guatemala and still hand over paper invoices, sooner or later a customer will ask for the electronic document and you will have to sort it out at the counter with a queue waiting. This guide covers what you need in order to issue FEL invoices from the point of sale, what changes at the till the day you turn it on, and what to do when something goes wrong.

What FEL is, and who actually certifies

FEL is the SAT's online electronic invoicing regime. On paper, the check happens afterwards: you issue the document and the information reaches the tax authority later. Under FEL it happens first. Every document is signed electronically and registered at the moment it is issued, and until that registration happens the document does not exist as an invoice.

That step is not done by your point of sale, and not by you: it is done by a certifier authorised by the SAT — a company the SAT has cleared to receive documents, validate them, and return them with an authorisation number.

FlowPOS issues FEL invoices through SAT-authorised certifiers. The distinction matters more than it looks: the point of sale assembles the document, sends it and stores the reply, but the authorisation comes from the certifier. If a vendor tells you they "certify invoices" without naming a certifier, ask which one they work with before signing anything.

What you need before you start

Four things, and it is worth having them ready before you touch any settings:

• Your company NIT and a settled tax regime. Pequeño Contribuyente and the general regime do not issue the same document types, and the regime is configured once.
• An active contract with a SAT-authorised certifier. It is contracted separately from the point of sale. Each has its own pricing, usually per bundle of documents or per month.
• The credentials that certifier issues you. A username, a password, and depending on the certifier a key or token as well. These are what connect your system to theirs.
• Your establishment details exactly as registered with the SAT. Address, trade name and establishment code. If they do not match what is registered, the certifier rejects the documents and the error only shows up when you try to invoice.

Order matters. Configuring the point of sale before the certifier contract exists means preparing the till to issue documents it does not yet have permission to issue.

What changes at the till

Less than people expect. Cashiers ring up the sale the same way: build it, pick the payment method, close. What changes is what comes out at the end. Instead of an internal receipt, you get a document carrying an authorisation number — and that number is what makes it a valid invoice.

There are three real changes to daily operations.

Ask for the NIT before closing, not after. The NIT is part of the document. If the customer offers it once you have closed, it is not a matter of correcting a slip: the document has to be voided and a new one issued. Asking before taking payment saves that step several times a day.

Receipts are no longer corrected, they are voided. A mischarged paper sale was torn up and redone. A FEL document is already registered, so the fix is a credit note or a void. Both leave a record, which is precisely the point.

The customer can receive it without paper. The electronic document is the original. The printed ticket is a courtesy, not the receipt. Plenty of businesses keep printing because customers ask for it, and that is fine — but paper no longer has to travel with the sale.

Credit notes and voids

Worth separating these, because they get confused often.

A void cancels the document. Use it when the sale should never have existed: it was invoiced twice, invoiced to the wrong customer, or the customer returned everything the same day. There is a time limit, and the SAT sets it, not your system.

A credit note corrects a document that legitimately existed. Use it for a partial return, a discount applied after the fact, or a wrong amount. The original document stays where it is and the note adjusts it.

The practical rule: if the whole sale should not have happened, void it. If the sale happened but the amount changed, issue a credit note.

What to watch in the first month

The three things most often discovered late:

1. Documents still waiting to be certified. If the connection dropped mid-afternoon, a document may be queued. Check at the end of the shift, not at the end of the month.
2. Final-consumer sales that should have carried a NIT. Usually business customers who did not give it in time. If there are many, the problem is not the system — it is when the question gets asked.
3. How fast you are consuming your certifier bundle. It is sold by document volume, and voids and credit notes are documents too.

Questions that always come up

What if the internet drops? The sale still records, and the document goes for certification once the connection returns. What you cannot hand over at that moment is the authorisation number, because it does not exist yet.

What if the customer has no NIT? It is issued to final consumer. That is a valid document and requires nothing from the customer.

Can I still print a ticket? Yes, and most businesses do. The printed ticket and the electronic document are not alternatives: one is the copy the customer takes away, the other is the record that exists with the SAT.

Do I need a new printer? No. FEL defines how the document is registered, not how it is printed. An ordinary thermal printer still works.

How long does it take? Seconds, on a healthy connection. A cashier should not notice a different wait from closing any other sale.

Where to start

If you are not invoicing electronically yet, the order that causes the fewest problems is: settle the regime with your accountant, contract the certifier, configure the point of sale with those credentials, and run a real test with a small sale before opening to the public.

The detail differs by business type. In a restaurant the NIT is best asked for when the table is opened, because the bill closes in a hurry; in a store it is asked at the till.

The part people underestimate is the last one. Configuration takes an afternoon; discovering at peak hour that the establishment code does not match the registered one takes the rest of the day.