Formal Obligations and VeriFactu

Mandatory Record Books

Every professional or business subject to VAT must maintain the following record books:

• Issued invoices register: all invoices you issue, with number, date, recipient, taxable base, VAT rate, and VAT amount.
• Received invoices register: all supplier invoices and deductible expenses.
• Capital goods register: for assets costing more than 3,005.06 euros (subject to VAT regularization over 5 years, or 10 for real estate).

For personal income tax under direct estimation, professionals must also keep an income book and an expenses book. Non-corporate self-employed must retain invoices and supporting documents for 4 years (the tax statute of limitations).

SII: Immediate Information Supply

The SII is an AEAT electronic system requiring invoicing records to be submitted within 4 calendar days of issuing or receiving an invoice. It is currently mandatory for:

• Large companies (turnover above 6,010,121.04 euros).
• VAT groups.
• Those enrolled in REDEME (Monthly Refund Register).

Small and medium-sized law firms are not required to use SII, unless they voluntarily opt for the monthly refund regime. However, understanding SII is essential for advising business clients who are obligated.

VeriFactu: The Major Change of 2026

Royal Decree 1007/2023, implementing the Anti-Fraud Law (Law 11/2021), establishes the VeriFactu (Invoice Verification) system. Key points:

• Requirement: all invoicing software used by businesses and professionals must be certified and guarantee the integrity, preservation, traceability, and immutability of invoicing records.
• Effective date: July 1, 2025 for the adapted software obligation. Software producers had to certify their solutions before that date.
• How it works: the software generates an invoicing record with an electronic signature (chained hash) that can be sent to the AEAT immediately (VeriFactu mode) or retained for submission upon request.
• Penalties: using non-certified software can result in fines of up to 50,000 euros per fiscal year.

For your firm: verify that your invoicing software complies with VeriFactu. If you use Excel or Word-based invoices, you need to migrate to a certified solution.

Form 347: Annual Declaration of Third-Party Transactions

Form 347 declares transactions with any third party that exceed 3,005.06 euros per year (VAT included). It is filed in February of the following year.

Key points for lawyers:

• If a client has paid you more than 3,005.06 euros in the year (totalling all invoices), you must include them.
• Intra-Community transactions declared on Form 349 are not included in Form 347.
• Errors in Form 347 are one of the main sources of AEAT inquiries, because it cross-references data between supplier and client.

Form 349: Intra-Community Transactions

If the firm provides services to EU business clients (or receives them), it must file Form 349 (recapitulative declaration of intra-Community transactions).

• Frequency: quarterly if transactions do not exceed 50,000 euros in the quarter or any of the previous four. Monthly if that threshold is exceeded.
• It is an informational form: it does not generate payment, but failure to file carries penalties.

Tax Calendar for the Firm

A summary of the main forms and deadlines for a typical firm:

Quarter	Forms	Deadline
Q1 (Jan-Mar)	303, 130, 111	April 1-20
Q2 (Apr-Jun)	303, 130, 111	July 1-20
Q3 (Jul-Sep)	303, 130, 111	October 1-20
Q4 (Oct-Dec)	303, 130, 111, 390	January 1-30
Annual	347, 349, 200	February, January, July