What does NRS actually check during an e-invoicing audit?

Four areas: whether a compliant system is in place and functioning, whether transaction records show all sales with valid IRNs and no transactions outside the system, whether TINs and data quality are correct, and whether invoices were validated and reported within required timeframes.

How far back can an audit look at my invoices?

Businesses are required to retain VAT and invoice records for a minimum of 6 years, which is generally the window auditors expect records to be available for.

What's the single most common audit finding for e-invoicing?

Missing or invalid TINs, incomplete mandatory fields, and transactions processed outside the e-invoicing system are the most common issues — most of which real-time validation catches before an invoice is ever submitted.

Can I prepare for an audit after receiving notice, or should preparation happen earlier?

Audit readiness should be continuous, not reactive. If your invoicing system validates every transaction at the point of issue and retains full records automatically, you're prepared by default rather than scrambling once notified.

Tax Invoice Audit Preparation: NRS Checklist Guide

An e-invoicing audit isn’t a single event to brace for once a year — it’s a check against records and processes that should already be in order. Knowing exactly what NRS examines makes the difference between “produce a report in minutes” and a multi-week scramble.

The Four Things NRS Actually Examines

1. System Implementation

Is a compliant e-invoicing system actually in place, when was it deployed, and is it functioning correctly? This is the baseline check — a business claiming compliance without a working, validated system in place fails here immediately.

2. Transaction Records

Do all sales have valid IRNs? Are B2C transactions properly reported? Are there any transactions processed outside the e-invoicing system entirely? Auditors are specifically looking for gaps — invoices that should exist but don’t, or that were handled manually to bypass the system.

3. Data Quality

Are TINs valid and verified for both supplier and buyer? Are all mandatory fields present? Are the tax calculations correct? Most audit findings come from this category — not fraud, just incomplete or unverified data.

4. Timing

Were B2B invoices validated before delivery to the buyer? Were B2C transactions reported within the required 24-hour window? Are credit notes properly linked to their original invoices? Timing violations are easy to miss day-to-day but show up clearly in an audit trail.

Preparing Before You’re Notified

Keep Records Audit-Ready by Default

The retention requirement is a minimum of 6 years across VAT invoices issued and received, credit and debit notes, import documentation, bank statements, and general ledger entries. See our full record-keeping guide for how to organize this so it doesn’t need last-minute assembly.

Verify TINs Continuously, Not Just at Onboarding

Since data quality is one of the four core audit checks, an outdated or unverified TIN discovered years later is still a finding today. See our TIN verification guide for the ongoing verification practices that keep this clean.

Validate Every Invoice Before Submission

Real-time validation — catching a missing field or invalid TIN before an invoice is submitted, rather than after rejection — prevents most of the data-quality findings auditors look for. See our guide to invoice validation errors and fixes for the specific failure patterns to guard against.

Don’t Process Anything Outside the System

Even occasional manual invoicing “just this once” creates exactly the transaction-record gap auditors are trained to find. If a system limitation is pushing you toward manual workarounds, that’s a signal to fix the integration, not to route around it.

What a Clean Audit Trail Actually Looks Like

A complete, audit-ready invoice record includes: the original invoice with all mandatory fields, its IRN and validation timestamp, the digital signature and QR code, any linked credit or debit notes, and delivery confirmation. If any one of these is missing, that’s the gap an audit will surface.

Get Audit-Ready Automatically

ZUTAX generates a complete compliance record for every invoice — IRN, validation timestamp, acknowledgement receipts, and linked corrections — stored for 6+ years with a full audit trail. If you’re audited, you can produce a complete compliance report in minutes instead of assembling one from scratch. Start your free trial and make audit prep a non-event.