About us

about us

Your time is valuable and better spent managing your
business. Why not leave your annual compliance
and other accounting needs in safe hands?


We’ll happily tailor our approach to suit your requirements. We offer a range of accounting
and tax services for businesses, individuals, trusts and rental property owners and more.

Owner guide
Accounting and Tax Services
Audit and Assurance
Cloud Accounting
Business Advisory Services and Strategy

We’re a firm of Chartered Certified Accountants, Chartered Accountants and Business Advisors based in Auckland with clients in New Zealand and overseas.

We’re determined to remain highly professional and approachable. We are big enough to cover clients’ needs but remain the right size to guarantee we still cover personal attention.  With Business Advisory Services, you are in safe hands.

We have a team with proven skills and experience, and the innovation to help you make good financial decisions to create success, value and prosperity.

Our Value
Our Mission
Our Vision

We take our “values” very seriously and set ourselves very high standards. In carrying out our obligations to you, work will be delegated to staff with the appropriate levels of skill and knowledge.
This enables us to remain efficient, without compromising our quality to you. However, I accept full responsibility for my team and I will remain the primary contact for you.

Mark Gwilliam FCCA CA – Director

Our mission is “to deliver consistent and excellent service to our clients; to offer rewarding careers and professional fulfilment for our teams; and to attain financial success so we can grow and prosper”.

We are determined “To be an international professional services company that helps our clients and people succeed in their busy working and personal lives”.


Mark Gwilliam

Director ~ Business Advisory Services and Risk Advisory Services

Mark is a Director in our Auckland office with extensive experience in New Zealand and overseas.


Mark started his career in the UK.  While there, he worked in numerous finances, operations, risk management, internal audit, and credit risk roles throughout the UK and Europe.

He moved to New Zealand in early 2001 and worked at Arthur Andersen and KPMG providing internal audit, governance and risk management services to executive management and boardrooms.

In early 2003, Mark established Business Advisory Accounting & Tax Services Limited.  He spends 25% of his time providing risk and internal audit services to New Zealand’s corporate sector.  The other 75% is spent consulting with owner-managed businesses providing tax advice, preparing financial statements and tax returns, and offering business advice.

Professional Credentials

Mark is a fellow of the Association of Chartered Certified Accountants (ACCA) and member of Australia and New Zealand Chartered Accountant (CAANZ) and holds Certificates of Public Practice with both.  He’s also a member of the Institute of Internal Auditors.

Personal Interests

Mark enjoys most types of sports, particularly cricket, football and rugby, albeit only as a spectator these days!  He’s an avid traveller and says he’s accumulated more than a fair share of trials and tribulations along the way.

Contact Mark at markg@bizadvice.co.nz

Mark Gwilliam

(Director and Founder)

40+ Years of Experience

37 Years of Experience

Dean Cross

Associate Director ~ Business Advisory Services and Financial Advisory Services

Dean is an associate director in both our Financial and Business Advisory Services.

He has extensive senior management experience in corporate finance and accounting roles. 

Dean brings a strong commercial acumen and perspective to a broad range of challenges faced by New Zealand’s Public Sector organisations.  His specialties lie in strategic financial modelling, finance department reviews, business cases, budgets and cost management reviews.

Previous Experience

Dean has more than twenty years’ senior experience in New Zealand’s Public Sector, primarily within health, but also with local councils and education providers.  He’s an approved Ministry of Health Business Case Reviewer and Lead Reviewer of two significant facility redevelopments. 

Dean was heavily involved in establishing and managing New Zealand’s largest shared services agency.  From preparing the original business case he later was appointed in senior management roles, including Interim CFO.

Professional Credentials

Dean is a member of Australia and New Zealand Chartered Accountants.  He holds a Bachelor of Business Studies from Massey University, majoring in Accounting and Finance.

Personal Interests

Dean enjoys a variety of team sports, particularly rugby, football and cricket, and is getting close to a single-figure golf handicap.

Contact Dean at Dean.Cross@bizadvice.co.nz

Dean Cross

(Associate Director)

A timeline of our history

Operating in New Zealand and exceeding clients’ expectations
for more than seventeen years

We’re extremely proud of our history and heritage as a firm of trustworthy business advisors and chartered accountants. 

From humble beginnings, the firm has grown from strength to strength. It has matured from being a small accounting and tax services practice
to one that now helps small business owners, entrepreneurs and executives navigate complex challenges including strategy, risk management and internal audit, managing shared-service centres and


January 2003

Mark establishes Business Advisory Services to provide tax and accounting services.

June 2007

We begin providing our new risk          advisory and assurance services                 to NZX listed organisations.

August 2012

We secure our first major risk         management and internal                             audit services contract                 with the health sector.

January 2014

We begin using Xero accounting           software for the first time

March 2017

Mark Gwilliam, FCCA CA, becomes a member of the Chartered Accountants Australia and New Zealand.

January 2018

Business Advisory Accounting & Tax Services Limited celebrate fifteen years as Auckland chartered accountants.

August 2019

We revise our eBook and publish “Tax Saving Strategies for Small-Business Entrepreneurs” and continue to offer it free of charge.

May 2001

Mark Gwilliam, FCCA, moves to                      New Zealand from the UK.

October 2004

Business Advisory Accounting & Tax Services Limited is formed.

August 2009

We launch our virtual Financial          Controller services to small to               medium sized businesses.

January 2013

Business Advisory Accounting & Tax Services Limited celebrate ten years as Auckland chartered accountants.

June 2016

Our global professional body, the Association of Chartered Certified Accountants (ACCA) announces a strategic alliance with the Chartered
Accountants Australia and New Zealand (CAANZ).

October 2017

We publish and offer our first edition of our eBook, “Tax Saving Tips”, free of charge.

September 2018

We extend our business advisory services and launch our virtual CFO services to small to medium sized businesses.

March 2020

We begin to offer fixed monthly          accounting fees for all of our                  annual tax compliance services.

Our clients are at the core of everything we do.

Business Advisory Services is the brand under which we provide
accounting and tax services, business risk management and internal
audit, and other tailored business advisory services.

Name withheld for privacy reasons

Proprietor, Small Pet Shop

I welcome this opportunity to thank Mark and his team for their help and support since I started my business. I thoroughly enjoy working with Business Advisory Services.

Name withheld for privacy reasons

Owner, Online Retailer

Mark Gwilliam has just completed the internal audit report of project governance. My staff and I commend him on his completely professional and engaging approach. He gave a fair view of project governance and by doing so added value to our function.

Name withheld for privacy reasons

General Manager, Large National Government Organisation

“Mark Gwilliam and his team at Business Advisory Accounting & Tax Services has been my full service accounting department for many years for my companies.
I rely on the fast, friendly and accurate information they provide me to analyse and concentrate on running my business. Any information that I need is readily available. To eliminate the costs and hassles of in-house accounting, I highly recommend Mark’s team.”

Name withheld for privacy reasons

Director, Medium Sized Building and Construction Business

Have a question or comment?


Please contact us with your enquiry. We will provide you with a personal response within one business day.

Contact us