Invoice Verification: Process, Mandatory Fields and German E-Invoicing Rules

Invoice verification is the control of incoming invoices before they are paid: are all mandatory fields present, are the figures correct, and was the service actually ordered and delivered? Digital invoice verification does this in software, without paper: invoices are captured automatically, checked against the mandatory fields of § 14 of the German VAT Act (UStG) and against purchase order and goods receipt, then approved digitally, fully documented and archived in line with GoBD.

Key points at a glance

• Definition: paperless, software-based checking, coding and approval of incoming invoices.

• Process: capture → formal check (§ 14 UStG) → factual check (3-way match) → detailed review and clarification → coding → approval → posting and archiving.

• Obligation: since 1 January 2025, businesses in Germany must be able to receive e-invoices; transition periods for issuing run until the end of 2026 or 2027.

• Retention: invoices 8 years (since 2025, previously 10).

• AI vs. OCR: AI understands any layout without templates; classic OCR does not.

What is digital invoice verification?

Digital invoice verification is the fully electronic control of incoming invoices, from capture through checking and coding to approval and posting, without paper and without manual typing. Software reads the invoice, checks the mandatory fields and matches the line items against purchase order and goods receipt. Clear-cut invoices run through without intervention; only exceptions reach a person. Every step is logged, so tax auditors and external auditors can trace the path of each invoice.

It differs from mere digitisation: a scanned or emailed PDF invoice is not digital invoice verification as long as data is retyped and approvals are collected by email. And under German VAT law a PDF is not an e-invoice: an e-invoice is a structured data set (XRechnung, or ZUGFeRD from profile EN 16931 upwards) that software can read without text recognition.

Formal, arithmetic and factual invoice verification

Every invoice check has several levels. The formal check verifies that the invoice contains all mandatory fields under § 14 (4) UStG and is correct for tax purposes. The arithmetic check usually belongs to it: are unit prices, quantities, subtotals, tax amount and total correct? The factual check establishes whether the goods or services were actually ordered, delivered and charged at the agreed price. Formal errors put input-tax deduction at risk; factual errors cost money directly. A digital solution runs all levels automatically and flags only the cases a person needs to decide.

Which mandatory fields must an invoice contain?

§ 14 (4) UStG lists ten mandatory fields. Digital invoice verification checks each of them automatically:

• Full name and address of the supplier and of the recipient (no. 1)
• Tax number or VAT ID of the supplier (no. 2)
• Issue date (no. 3)
• Sequential invoice number, assigned once (no. 4)
• Quantity and type of goods, or scope and type of service, in customary terms (no. 5)
• Date of supply or service, where applicable the month of service (no. 6)
• Net amount, broken down by tax rate and exemption, plus any reduction agreed in advance such as early-payment discounts or rebates, unless already included (no. 7)
• Tax rate and tax amount, or a note on the exemption (no. 8)
• Note on the recipient's retention obligation where the recipient is not a business and the service relates to real estate (no. 9)
• The word "Gutschrift" (self-billing) where the recipient issues the invoice (no. 10)

Small-amount invoices up to EUR 250 gross need fewer fields (§ 33 UStDV): supplier name and address, issue date, quantity and type of service, gross amount and tax rate. Good verification software detects the amount and applies the matching rule set. The full list with examples is in the mandatory-fields checklist.

What happens if fields are missing or the invoice is wrong?

A missing or incorrect mandatory field puts the input-tax deduction at risk (§ 15 UStG). This often surfaces years later in a tax audit, when the tax office reclaims the input tax plus interest. With high invoice volumes, small formal errors add up quickly.

A faulty invoice is therefore not paid but rejected or returned for correction. The supplier corrects missing or wrong fields with a document that refers unambiguously to the original invoice (§ 31 (5) UStDV). For factual errors such as wrong quantity or price, the supplier issues a corrected invoice or credit note. In digital invoice verification, the software generates the feedback to the supplier with the specific finding, instead of someone explaining the error by email.

Who is responsible for invoice verification?

Accounts payable usually handles the formal and arithmetic check, the department that ordered the service handles the factual check. Approval is given by the budget owner, often in several stages depending on the amount. The four-eyes principle with segregation of duties applies: whoever checks does not approve alone, and whoever creates suppliers does not release payments. A digital solution maps these roles as a workflow, including delegation rules for holidays and sick leave and mobile approval, so no invoice gets stuck in the inbox of someone who is away.

The invoice verification process step by step

1. Capture: the invoice arrives by email, portal, scan or as XRechnung or ZUGFeRD. Structured e-invoices are read directly, PDFs and scans are extracted with AI, without templates per supplier. Duplicates are caught at this stage.
2. Formal and arithmetic check: the software checks the ten mandatory fields, tax rate and tax amount, all totals and the VAT ID. At the same time it runs a master-data check: do supplier, address and bank details match the vendor master? A changed IBAN is a classic fraud pattern and is stopped.
3. Factual check (3-way match): invoice, purchase order and goods receipt or proof of service are matched line by line: quantity, unit price, terms. If price or quantity differ, a tolerance rule decides (for example accept automatically up to 1 % or EUR 5, above that clarify). Without a purchase order, for example for services, the invoice goes to the department for confirmation.
4. Detailed review and clarification: line items with discrepancies or special contract terms are reviewed in detail. The software clarifies open points with the people involved in the workflow: a query to the department, to purchasing or directly to the supplier. Every query and answer stays documented on the document.
5. Coding: general-ledger account, cost centre and, where relevant, project are assigned. The software proposes the coding based on earlier invoices from the same supplier; a person only confirms exceptions.
6. Approval: clear-cut invoices within the rules are approved automatically, all others go to the responsible person, with the four-eyes principle for higher amounts. Early-payment discount deadlines are monitored and prioritised.
7. Posting, payment and archiving: the verified data set goes into the ERP (SAP, DATEV or others), is passed to the payment run and archived unalterably. How to automate this chain end to end is shown in automate invoice verification with AI.

What are the benefits of digital invoice verification?

• Faster: processing time per invoice from minutes to seconds, cycle time from days to hours.
• Discounts instead of late fees: approving invoices within a few days lets you take early-payment discounts and avoid dunning fees and late-payment interest. For many companies this is the single biggest lever.
• Fewer errors: automatic checks of mandatory fields and totals, duplicate and fraud detection.
• Audit-proof: complete, GoBD-compliant documentation of every check.
• Scalable: high volumes and many suppliers without additional staff.
• Transparent: status, approval path and open liabilities visible at any time.

What does digital invoice verification deliver?

In practice, companies using AI-based digital invoice verification achieve typical effects:

• Touchless processing: up to 80 % without manual intervention
• Processing time: seconds instead of minutes per invoice
• New invoice type live: in minutes instead of days, without a template
• Errors, duplicates and fraud: significantly reduced through automatic checks

Worked example: what changes in a mid-sized company

Fictitious example with assumed values for illustration, not a customer measurement. Recalculate with your own figures.

An industrial company receives 2,000 incoming invoices a month with a volume of EUR 1.5 million. Manually, accounts payable needs 10 minutes per invoice on average: around 330 working hours a month. Many suppliers grant a 2 % discount for payment within 14 days, but because of long approval paths it is taken on only 40 % of the volume.

After the switch, an assumed 70 % of invoices run through without intervention. The remaining 600 invoices are exceptions that arrive prepared with all findings and take around 4 minutes: about 40 working hours. Because approvals now happen within a few days, the discount rate in the example rises to 85 %. Additional discount: 45 % of EUR 1.5 million times 2 %, roughly EUR 13,500 a month, plus around 290 working hours saved.

The values vary widely with invoice mix, purchase-order coverage and supplier terms. We are happy to calculate the business case for your real invoices together in a demo.

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Requirements for digital invoice verification

• E-invoice capability: XRechnung and ZUGFeRD must be received and processed (deadlines below).
• GoBD compliance: audit-proof, unalterable storage and logging.
• Clean master data: a maintained vendor master with bank details, purchase orders and goods receipts in the ERP.
• Data protection: GDPR-compliant processing, ideally operated in Germany.
• Clear rules: § 14 UStG, tolerances, coding rules, approval levels and the four-eyes principle.

E-invoicing in Germany: which deadlines apply?

The B2B e-invoicing mandate is the main driver of digital invoice verification in Germany. The deadlines follow from § 14 (1) and § 27 (38) UStG:

• Since 1 January 2025: all businesses in Germany must be able to receive e-invoices. There is no transition period for receiving.
• Until 31 December 2026: paper and PDF invoices may still be issued (PDF only with the recipient's consent).
• Until 31 December 2027: businesses with prior-year turnover of no more than EUR 800,000 may continue to issue paper or PDF; EDI procedures remain permitted with the recipient's consent.
• From 1 January 2028: only e-invoices are permitted for domestic B2B transactions as a rule (exceptions include small-amount invoices up to EUR 250).

Details on formats and exceptions are in our article on the e-invoicing mandate in Germany 2025 to 2028.

How long must invoices be retained?

Since 1 January 2025, invoices and accounting vouchers must be retained for eight years instead of ten (§ 14b (1) UStG, § 147 (3) AO). The shorter period applies to all invoices whose old period had not expired by the end of 2024. Credit institutions, insurers and investment firms benefit one year later: for them the new period applies only to documents whose old period was still running on 1 January 2026 (§ 27 (40) UStG). The period starts at the end of the calendar year in which the invoice was issued. E-invoices must be retained in their original format, as a structured data set.

Challenges when introducing it (and how AI solves them)

• Inconsistent formats: hundreds of suppliers with their own layouts. AI understands every layout without a template instead of maintaining templates.
• Existing ERP landscape: the solution must fit into SAP, DATEV and the DMS rather than replace them. See invoice verification with SAP & DATEV.
• Team acceptance: staff only review exceptions; clear workflows and full traceability build trust.
• Proof of compliance: GoBD-compliant, audit-proof logging and data protection (GDPR, operation in Germany) must be in place from day one.

Digital invoice verification with AI instead of classic OCR

Many "digital" solutions still work with templates per supplier. When a layout changes, recognition breaks. An AI solution understands every invoice by its content, including unknown layouts, and learns from every correction. Why templates fail is explained in OCR vs. AI extraction.

THE MODERN APPROACH: Digital invoice verification, fully automated with AI

The ADVISORI AI Invoice Verifier captures every invoice without a template, checks § 14 UStG, 3-way match, duplicates and fraud, and approves clear-cut documents automatically. GoBD-compliant, integrated with SAP and DATEV, operated in Germany.

Explore the solution →

Which software for digital invoice verification?

The market offers AI-based software, classic OCR tools, ERP modules (SAP, DATEV), DMS solutions and pure e-invoice validators. Key selection criteria: processing of XRechnung and ZUGFeRD, recognition without templates, 3-way match with tolerance rules, coding proposals, configurable approval workflows with delegation, an interface to your ERP and GDPR-compliant operation. Which type fits which need is shown in the invoice verification software comparison. For ERP integration see invoice verification with SAP & DATEV.

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Digital invoice verification and data protection

Invoices contain personal and sensitive business data. Digital invoice verification must therefore work in a GDPR-compliant way: clear access rights, complete logging and ideally on-premise or trusted-region hosting, so invoice and personal data never leave your infrastructure. GoBD compliance and GDPR work hand in hand.

Trends: where digital invoice verification is heading

• From OCR to AI: template-free models are replacing rule-based text recognition.
• E-invoicing as the standard: with the e-invoicing mandate 2025 to 2028, structured formats (XRechnung, ZUGFeRD) become the norm.
• Real time and touchless processing: more and more invoices are checked and approved without human intervention.
• Built-in compliance: GoBD, GDPR and the EU AI Act are considered directly in the verification process.

Frequently asked questions (FAQ)

What is invoice verification?

The control of incoming invoices before payment: checking the mandatory fields under § 14 UStG, the arithmetic and whether the goods or services were actually ordered and delivered. Digital invoice verification does this in software, including coding, approval and GoBD-compliant archiving.

How does the invoice verification process work?

Capture, formal and arithmetic check with master-data matching, factual check via 3-way match, detailed review and clarification of discrepancies, coding, approval under the four-eyes principle, then posting, payment and archiving. With AI, clear-cut cases run fully automatically.

What is the detailed review ("Subprüfung") in invoice verification?

The in-depth check of individual line items or special contract terms, and the clarification of discrepancies with those involved, such as the department, purchasing or the supplier. In digital invoice verification it runs as a documented query workflow on the document.

Is digital invoice verification mandatory in Germany?

The verification itself is not prescribed. Since 1 January 2025, however, businesses must be able to receive e-invoices and retain them in their original format, and from 2027 or 2028 they must also issue them. Digital verification is therefore the practical standard.

How long must invoices be retained in Germany?

Eight years since 1 January 2025 (§ 14b UStG, § 147 AO), previously ten. For banks, insurers and investment firms the shorter period applies one year later.

What applies to small-amount invoices?

Up to EUR 250 gross, supplier name and address, issue date, quantity and type of service, gross amount and tax rate are sufficient (§ 33 UStDV).

What should I do with a faulty invoice?

Do not pay it; reject it or request a correction. The supplier adds missing fields with a document that refers unambiguously to the original invoice; for wrong quantities or prices they issue a corrected invoice or credit note.

What are the benefits of digital invoice verification?

Shorter processing and cycle times, early-payment discounts taken, lower cost per document, fewer errors through automatic checks, duplicate and fraud detection, audit-proof documentation and scalability at high volume.

About ADVISORI FTC GmbH: AI-based, GoBD- and GDPR-compliant digital invoice verification, operated in Germany.