Sonntag & Partner

What Sonntag & Partner does

Sonntag & Partner is a German multidisciplinary professional services firm (Wirtschaftskanzlei) headquartered in Augsburg and operating across four offices in Augsburg, Munich, Ulm, and Nuremberg. Founded in 1978 by Dieter Sonntag as a solo tax and audit practice, the firm has grown to approximately 500 professionals providing integrated tax advisory (Steuerberatung), legal counsel (Rechtsberatung), and economic audit (Wirtschaftsprüfung) services. Its target market is the German upper mid-market (gehobener Mittelstand), typically family-owned and entrepreneurial businesses, including private equity investors, that require coordinated multidisciplinary advisory for M&A, restructuring, succession, and regulatory compliance matters.

The firm's service offering is extended through wholly owned affiliated brands covering Family Office wealth management (Sonntag-FO), asset management advisory (Sonntag-VB), IT audit and consulting including e-invoicing compliance (Sonntag-ITS), and digital tax advisory (Sonntag-SmartTax). Specialized advisory practices have been added in recent years in industrial property rights, energy economics and climate protection, data protection, public procurement law, and NIS-2 cybersecurity compliance. International cross-border work is delivered through the MOORE International network. The firm is structured as a German partnership (Partnerschaftsgesellschaft mbB) under private ownership, with no external institutional or PE investor disclosed.

Revenue is generated primarily through professional services fees on an engagement-by-engagement basis, with project-based and recurring client relationships across the three core disciplines. Client acquisition is sales-led and referral-driven, supported by thought leadership including webinar series (Tax Talk, Tax Tuesday), publications, and industry event participation. Notable mandates include advising Waterland on the Strobel Group acquisition (2021), Bühler Motor on the sale of Bühler Motor Aviation to Astronics (2025), the SAG sale to IB Regehr & Völker (2026), the Allgäu Fresh Foods restructuring (preserving 360 jobs), and advising Hessing Stiftung on the Gut Güttin asset transaction.

Name

Sonntag & Partner

Legal name

Sonntag & Partner Partnerschaftsgesellschaft mbB

Website

https://sonntag-partner.de

Company type

Private

Founded year

1978

Operating status

Operating

Headcount range

251–500 employees

Short description

Sonntag & Partner is a German multidisciplinary professional services firm (Wirtschaftskanzlei) headquartered in Augsburg with ~500 professionals across four offices, providing integrated tax advisory, legal, and audit services to upper mid-market companies and private equity clients.

Ownership category

akta.pro rank

Product category

Professional Services (Tax, Legal, Audit)

NAICS

Legal Services (5411), Accounting, Tax Preparation, Bookkeeping, and Payroll Services (5412), Offices of Certified Public Accountants (541211)

SIC

Services-Legal Services (8111), Services-Management Consulting Services (8742), Services-Management Services (8741)

akta.pro primary industry

Transaction Tax Structuring & Deal Advisory (BPAHAOAJ)

akta.pro secondary industries

Tax Planning & Compliance for Family Offices (FSAAADAE), Family & Private Client (Trusts & Estates) Law (BPAHAAAK), Closing Coordination & Transaction Management (Broker/Agent Support) (BPAJAOAH)

Keywords

• Tax advisory services
• Legal consulting
• Audit services
• M&A advisory
• Corporate restructuring

Headquarters

HQ city

Augsburg

HQ country

Germany

HQ region

Europe

Offices4 records

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Operations, Marketing or Sales, Infrastructure, Technology or R&D

Revenue model

1. Professional Services (Tax, Legal, Audit): Fees generated from tax advisory, legal counsel, and economic audit engagements. Revenue is primarily project-based and recurring client relationships across a multidisciplinary service offering.

Go-to-market motion1 record

Distribution channels1 record

Marketing channels4 records

Core offering

Sonntag & Partner is a multidisciplinary Wirtschaftskanzlei offering integrated tax advisory (Steuerberatung), legal counsel (Rechtsberatung), and economic audit (Wirtschaftsprüfung) services. The firm serves the upper mid-market segment with single point-of-contact coordination across all three disciplines, complemented by affiliated entities providing Family Office/wealth management, IT solutions, digital tax advisory, and specialized compliance services such as NIS-2 and e-invoicing.

Product overview

Sonntag & Partner is a mid-sized multidisciplinary professional services firm (Wirtschaftskanzlei) offering an integrated suite of audit, tax advisory, and legal services. The core offering spans three pillars: Steuerberatung (tax advisory), Rechtsberatung (legal services), and Wirtschaftsprüfung (audit). These are complemented and extended by affiliated service brands covering Family Office/wealth management (sonntag-fo.de), asset management advisory (sonntag-vb.de), IT solutions and e-invoicing compliance (sonntag-its.de), and digital tax advisory (sonntag-smarttax.de). The firm also delivers specialized advisory services including NIS-2 cybersecurity compliance, M&A due diligence, succession planning, and real estate transaction support, all coordinated across offices in Augsburg, Munich, Ulm, and Nuremberg with approximately 500 employees.

Differentiator

Problem solved

Functional benefit

Products and services

• Steuerberatung (Tax Advisory) Tax advisory services covering national and international tax planning, structuring, and compliance for corporate and individual clients.
• Rechtsberatung (Legal Services) Comprehensive legal advisory across multiple practice areas including corporate law, M&A, employment law, real estate law, and IT/IP law.
• Wirtschaftsprüfung (Audit Services) Auditing services including annual and consolidated financial statement audits, due diligence reviews, and valuation services.
• M&A | Due Diligence Advisory M&A advisory and due diligence services accompanying clients through all phases of buy-side and sell-side transactions.
• NIS-2 Beratung (NIS-2 Compliance Advisory) Advisory services on the EU NIS-2 Directive cybersecurity requirements, helping clients assess applicability and achieve compliance.
• E-Invoicing Compliance Advisory (E-Rechnungspflicht)

Quantifiable outcome

• 360 jobs preserved through Allgäu Fresh Foods restructuring
• +1 more outcomes

Named customers6 records

Segments1 record

Ideal customer profiles2 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Partnerships

One partnership is on record.

• MOORE InternationalcoreTechnology or IntegrationSONNTAG provides services internationally through the MOORE network, a global accounting and advisory network, enabling cross-border advisory capabilities for clients.

Scale indicators4 records

Recent moves7 records

Expansion highlights5 records

Direct peers

• Ebner Stolz: Ebner Stolz is one of Germany's largest independent multidisciplinary advisory firms offering audit, tax, legal, and consulting services to mid-market companies, with comparable client profile, partner-led model, and integrated service offering.
• Rödl & Partner: Rödl & Partner is a German-headquartered multidisciplinary professional services firm combining legal, tax, audit, and advisory services, with a particularly strong presence in Bavaria — the closest direct competitor to Sonntag & Partner in terms of model, geography, and Mittelstand client focus.
• Mazars Germany: Mazars operates an international integrated audit, tax, and advisory practice with a notable German Mittelstand offering, directly competing with Sonntag for upper mid-market mandates across advisory disciplines.
• BDO Germany: BDO is a global accounting and advisory network with substantial German mid-market presence spanning audit, tax, and consulting — directly comparable network-based multidisciplinary model targeting Mittelstand clients.
• Flick Gocke Schaumburg: Flick Gocke Schaumburg is a top German advisory firm specializing in tax law and closely integrated corporate legal advice for major corporations and Mittelstand — directly comparable to Sonntag in the tax-law combination and upper mid-market positioning.
• RSM Germany: RSM Germany is part of the RSM international advisory network, providing audit, tax, and consulting services to mid-market companies — directly comparable network affiliation and Mittelstand client orientation.
• Warth & Klein Grant Thornton: Warth & Klein Grant Thornton is a top-10 German audit, tax, and advisory firm with a strong Mittelstand focus — directly comparable in client segment and integrated service delivery.
• Baker Tilly Germany: Baker Tilly is an international accounting and advisory network with a strong German mid-market practice combining audit, tax, and legal services — comparable mid-tier multidisciplinary model and Mittelstand client focus.

Broad incumbents

• Deloitte Germany: Deloitte is a Big 4 firm with comprehensive audit, tax, legal, and consulting practices in Germany — overlaps Sonntag's multidisciplinary model but with substantially broader capability and global reach.
• KPMG Germany: KPMG is one of the Big 4 globally and a major competitor in Germany across audit, tax, and advisory — overlaps Sonntag's offerings as part of a much broader portfolio including consulting and deal advisory at the largest enterprise scale.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat3 records

Key risks6 records

Key highlights7 records

Customer concentration

Revenue estimate

Valuation estimate

Number of profiles

Profiles16 records

Subsidiaries5 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Sonntag & Partner