My sense is that экспертирование is a broad term that can involve reviewing documents, drawing up opinions, etc. I would go for something broad like "consulting."

..

налоговая экспертиза+консультирование?

“Экспертирование” употребляется как минимум в двух значениях

1. Работа экспертов (как процесс) по проведению экспертиз, см. http://fip.kpmo.ru/fip/info/13449.html или http://gendocs.ru/v38209/лекция-_прогнозирование,проектирова...
2. Консультирование, выполняемое экспертами относительно экспертных или иных заключений, отчетов, просто документов, см. http://lev-group.ru/legal/, или http://www.ul-rabota.ru/resume-16923.html

Может быть, под "налоговым" экспертированием (поиск коего через гуглы дает ссылки только на эту страницу), имеются в виду консультации эксперта (юриста, банковского работника и т.п.) относительно именно и в частности налоговых экспертиз?

Примеры употребления tax due diligence consulting:
...where he was responsible for performing both financial and tax consulting services to a variety of foreign investors as well as tax due diligence consulting services of a number of merger and acquisition deal structures for potential buyers см. (http://www.hkexnews.hk/listedco/listconews/sehk/2009/1215/00...

E. J. McKay acted as the financial advisor, CMS the legal advisor, and Deloitte & Touche as the financial and tax due diligence consultant
(http://globenewswire.com/news-release/2012/12/20/513045/0/en...

Shawn also provides consulting on tax due diligence and structuring for M&A transactions.
http://www.tgccpa.com/shawnhoward.php

Вообще хорошо бы справиться в том самом банке, что конкретно имеется ввиду.

The determination of how much a person or company owes in taxes. One usually determines one's own tax assessment by declaring one's income and capital gains from the previous year and applying the methodology the government requires to arrive at the tax liability.
Before self assessment was introduced, the Inland Revenue calculated your tax and then issued a tax assessment showing any tax you owed. These types of assessments are now not normally issued. An assessment may be issued if you have omitted income from your Tax Return if the deadline for raising enquiries by the Inland Revenue has passed.
http://www.taxpenny.co.uk/tax-glossary.html

http://www.mutualfundsindia.com/tracker_supreme.asp
http://blog.mytaxzone.com.au/2010/03/2010-income-tax-assessm...
https://www.nordisketax.net/main.asp?url=files/nor/eng/i06.a...
http://museumvictoria.com.au/collections/items/1125190/taxat...


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Note added at 1 day8 hrs (2013-01-11 08:09:36 GMT)
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Difference between Tax Assessment and Tax consulting (in extent of mandatory):

"Tax Assessment" has much more extent of mandatory than "Tax consulting" that just required for giving expert advice within a taxation field.

Assessment:
the act of assessing or an amount (of tax, levy or duty etc) assessed;
http://en.wiktionary.org/wiki/assessment
To calculate and demand (the tax money due) from a person or entity; To impose or subject to (taxation and legal)
"Once you've submitted a tax return, the Tax Department will assess the amount of tax you still owe".
http://en.wiktionary.org/wiki/assess

Before self assessment was introduced, the Tax Department calculated your tax and then issued a tax assessment showing any tax you owed. The tax assessment may be issued if you have omitted income from your Tax Return;
Then a Tax Assessment Notice issued by the same competent authority is always followed by the concluded Tax Assessment.
http://blog.mytaxzone.com.au/2010/03/2010-income-tax-assessm...

Consultancy:
the practice of giving expert advice within a particular field; The act or an instance of consulting that offering expert or professional advice in a field;
A consultant who is engaged in Consultancy (from Latin: consultare "to discuss") is a professional who provides professional or expert advice[1] in a particular area such as security (electronic or physical), management, accountancy, law (tax law, in particular), human resources, marketing (and public relations), finance, engineering, or any of many other specialized fields.
http://en.wikipedia.org/wiki/Consultancy
In a business environment, consultants are often used to create the functional specifications from which vendors can respond. Consultants typically come from third party consulting firms or self-employed individuals and engages with multiple and changing clients. Consultants work at client places on behalf of a consultancy or Billing company. Some consultants are individuals hired by companies to do work for them on a contractual basis. They are not employees of the company hired to do a specific work. They are expected to do their job ethically and responsibly with minimum supervision.
A tax advisor is a financial expert specially trained in tax law. Some countries require tax advisors to verify the balance sheets of companies above a certain size. Individuals usually require tax advisors to minimize taxation, to avoid learning the details of tax law in complicated financial situations themselves or to learn the details of tax law from a professional advisor.