These are the words you will meet as your business moves to NRS e-invoicing, each explained in a few sentences. If we cover a term in more depth elsewhere, its definition links there. New to the topic? Start with our guide to NRS e-invoicing.
NRS (formerly FIRS)
The Nigeria Revenue Service, formerly FIRS, is the tax authority that runs e-invoicing. Every e-invoice your business issues is reported to it. Guides that still say "FIRS e-invoicing" mean the same thing. More
E-invoicing
E-invoicing is the system the NRS is moving VAT-registered businesses onto. Every invoice is checked, given an IRN and a QR code, and reported to the NRS. Our guide sets out which businesses must start and when. More
MBS (Merchant Buyer Solution)
The MBS is the NRS's e-invoicing system. Invoices are reported to the NRS through it, and it passes them on to the buyer's access point. Businesses do not connect to it directly. They connect through a licensed Access Point Provider. More
IRN (Invoice Reference Number)
The IRN is the number that identifies an invoice to the NRS. It joins three parts with dashes: your invoice number (letters and digits only), your 8-character NRS Service ID and the invoice date written as year, month, day. For example: INV001-94ND90NR-20260929. Yona builds it for you, and each IRN must be unique, so every invoice needs a new invoice number. More
QR code
A QR code is a square barcode on each e-invoice. It is made with your business's own NRS crypto key once the NRS has registered the invoice. Print both the IRN and the QR code on every copy of the invoice. More
TIN (Tax Identification Number)
Your TIN is the number that identifies your business for tax. You verify your business with its TIN when you sign up to Yona. Yona also uses a buyer's TIN to check whether they are on the e-invoicing network. More
Business ID
Your Business ID identifies your business on the NRS e-invoicing portal. You copy it from My Account, then API Integration, and enter it in Yona when you click Connect. More
Service ID
Your Service ID is an 8-character code the NRS issues to your business, such as 94ND90NR. It is the middle part of every IRN you issue, and on the NRS portal you find it in the IRN Template, between the two dashes. It is not the same as Elyonar's licence numbers. More
Crypto key
Your crypto key is a file your business gets from the NRS portal, under Manage Cryptographic Keys. You upload it when you click Connect in Yona, so your invoices can be signed as your business and carry their QR code. If you already have a key, choose Re-download Key rather than generating a new one, because a new key can replace one that works. More
Access Point Provider (APP)
An APP is a company licensed by NITDA to carry invoices between businesses and the NRS. It signs, sends and receives e-invoices on your behalf, and you choose yours on the NRS e-invoicing portal. Elyonar LTD, the company behind Yona, is one (licence NITDA/2026/A3HXS0). More
System Integrator (SI)
An SI is a company licensed by NITDA to connect a business's own accounting, billing or ERP (business management) software to e-invoicing. Elyonar holds this licence too (NITDA/2026/S21ZW0), so the same company can connect the systems you already run and carry your invoices. More
E-invoicing network
The e-invoicing network is the NRS e-invoicing system together with the licensed access points connected to it. An invoice travels from the seller's access point, through the NRS, to the buyer's access point. In Yona you can follow each step as it happens. More
Buyer on or off the network
A buyer is on the network when their business has chosen an access point, and your invoice then goes straight to their system. A buyer off the network gets the invoice from Yona by email or a share link instead, and it is still reported to the NRS. Yona checks your buyers for you, so you know which way an invoice will go before you send it. More
Validation
Validation is the check of an invoice against the NRS format and rules. Yona validates every invoice before reporting it, and you can also check one on its own first without sending anything to the NRS. If the NRS refuses an invoice, the reasons come back so you can correct it and submit it again. More
Reported invoice
A reported invoice is one the NRS has registered with its IRN. From then on its content is final and cannot be edited. You can still update its payment status, and you fix a mistake with a credit or debit note. More
Received invoice
A received invoice is one another business has issued to you through the e-invoicing network. Once you choose Elyonar as your Access Point, these invoices arrive in Yona with their totals and input VAT (the VAT charged to you on purchases). Your earlier invoices held by the NRS come in too. More
Credit note
A credit note cancels an invoice you have already reported, or reduces what is owed on it. A reported invoice can never be edited, so this is how you correct it. The credit note refers to the original invoice by its IRN and is reported to the NRS too. More
Debit note
A debit note changes the amount owed on an invoice you have already reported, usually to add to it, without cancelling the original. Like a credit note, it refers to the original invoice and is reported to the NRS. More
Sandbox
The sandbox is Yona's practice mode. It runs the real flow against the NRS test system, has no legal effect, and is free, with a separate allowance of test credits that refills every month. To set it up, turn TEST MODE on in the NRS portal. Keys made in test mode work only in the sandbox. More
Credits (Yona)
Credits are the unit Yona's plans are counted in. Each plan grants credits every month, and each action, such as reporting an invoice, uses a set number of them. Viewing and the automatic status and buyer checks are free. A credit is a unit, not a sum of money, and you can top up in the app at any time. More