In the
 United States Court of Appeals
               For the Seventh Circuit
                          ____________

Nos. 02-3914, 02-3915
UNITED STATES OF AMERICA,
                                                  Petitioner-Appellee,
                                  v.


BDO SEIDMAN, regarding promoter
examination of BDO SEIDMAN,
                                                Respondent-Appellee.


APPEALS OF: JOHN DOE and
JANE DOE and RICHARD ROE and
MARY ROE,
                                                Proposed Intervenors.
                          ____________
            Appeals from the United States District Court
        for the Northern District of Illinois, Eastern Division.
               No. 02 C 4822—Milton I. Shadur, Judge.
                          ____________
        ARGUED MAY 30, 2003—DECIDED JULY 23, 2003
                          ____________


  Before RIPPLE, KANNE and WILLIAMS, Circuit Judges.
   RIPPLE, Circuit Judge. Several unnamed clients of BDO
Seidman, LLP (“BDO”), a public accounting and consulting
firm, appeal from the district court’s denial of their motions
2                                     Nos. 02-3914, 02-3915

to intervene in an Internal Revenue Service (“IRS”) enforce-
ment action against BDO.
   The IRS had issued twenty summonses to BDO as part of
its investigation of BDO’s compliance with Internal Revenue
Code registration and list-keeping requirements for or-
ganizers and sellers of potentially abusive tax shelters. See
26 U.S.C. §§ 6111, 6112. The clients sought to intervene to
assert a confidentiality privilege regarding certain docu-
ments that BDO intended to produce in response to those
summonses. The clients argued that, because these docu-
ments reveal their identities as BDO clients who sought ad-
vice regarding tax shelters and who subsequently invested
in those shelters, disclosure inevitably would violate the
statutory privilege protecting confidential communications
between a taxpayer and any federally authorized tax prac-
titioner giving tax advice. See 26 U.S.C. § 7525. For the rea-
sons that follow, we affirm the district court’s denial of the
clients’ motions to intervene.


                              I
                     BACKGROUND
A. The Enforcement Action
  In September 2000, the IRS received information suggest-
ing that BDO was promoting potentially abusive tax shelters
without complying with the registration and listing re-
quirements for organizers and sellers of tax shelters. See 26
U.S.C. §§ 6111, 6112. Section 6111(a) of the Internal Revenue
Code requires organizers of tax shelters to register the tax
shelter with the IRS. See 26 U.S.C. § 6111(a). Any tax shelter
required to be registered under § 6111, as well as any
“arrangement which is of a type which the Secretary
determines by regulations as having a potential for tax
Nos. 02-3914, 02-3915                                       3

avoidance or evasion,” is considered to be “potentially abu-
sive.” 26 U.S.C. § 6112(b). Accordingly, the organizers and
sellers of such tax shelters must keep a list identifying each
person to whom an interest of the tax shelter was sold. See
26 U.S.C. § 6112(a). Failure to comply with the registration
and listing requirements of § 6111 and § 6112 can lead to the
imposition of penalties. See 26 U.S.C. §§ 6707, 6708. Because
the IRS suspected that BDO had violated these statutory
provisions by organizing and selling interests in potentially
abusive tax shelters without complying with the registration
and list-keeping requirements, it issued a series of sum-
monses to BDO, identifying twenty types of tax shelter
transactions in which it suspected that BDO’s clients had
invested.
   The summonses command production of documents and
testimony relating to the identified transactions, as well as
information about BDO clients who invested in the identi-
fied tax shelters. For example, the summonses demand doc-
uments identifying the investors in the transactions, the date
on which those investors acquired an interest, and all tax
shelter registrations filed and investor lists prepared with
respect to the transactions.
  In July 2002, when BDO failed to produce documents as
required by the summonses, the IRS petitioned the district
court for enforcement. BDO opposed enforcement. It ar-
gued that the investigation did not have a legitimate pur-
pose, that the summonses were overbroad and issued in
bad faith, and that the information sought was already in
the possession of the IRS and was not relevant to the inves-
tigation. BDO also claimed that some of the summoned
information was protected from disclosure by the attorney-
client privilege, the work product doctrine, and the confi-
dentiality privilege of § 7525 of the Internal Revenue Code.
In October 2002, the district court ruled that the IRS had
4                                    Nos. 02-3914, 02-3915

met its burden of showing that it issued the summonses in
good faith, and that BDO had failed to show that enforce-
ment of the summonses would constitute an abuse of proc-
ess. See United States v. BDO Seidman, LLP, 

, 920 (N.D. Ill. 2002). The district court then directed
BDO to produce, on or before November 4, 2002, all re-
sponsive documents except those that BDO previously had
listed on privilege logs and submitted to the court for an in
camera review.


B. The Motions to Intervene
   Among the responsive documents not previously
submitted for the court’s in camera inspection were records
that reveal the identities of the BDO clients who invested
in at least one of the 20 types of tax shelters identified in
the summonses. BDO informed its clients that it intended
to produce these documents to the IRS. In response, two
sets of unidentified taxpayers—the John and Jane Does and
the Richard and Mary Roes (hereinafter referred to collec-
tively as “the Does”)—filed emergency motions to inter-
vene in the enforcement proceedings pursuant to Federal
Rule of Civil Procedure 24(a)(2). The Does, asserting that
they are BDO clients who sought BDO’s confidential advice
regarding the potential tax effects of certain proposed
financial transactions, argued that the documents revealing
their identities are privileged under 26 U.S.C. § 7525, and
that BDO was not adequately representing their interest in
keeping that information confidential. The Does conceded
that, aside from the fact that the documents reveal their
identities as BDO clients who invested in at least one of the
20 types of tax shelters described in the summonses, the
documents themselves do not contain any otherwise priv-
ileged communication. After a hearing, the district court
denied the Does’ emergency motions to intervene. The
Nos. 02-3914, 02-3915                                      5

court concluded that information regarding a client’s iden-
tity falls outside the scope of the § 7525 privilege. Because
the district court did not believe that the Does would have
a likelihood of success on the merits of an appeal, it denied
the Does’ motion for a stay of its enforcement order.
  The Does filed timely notices of appeal from the denial of
their motions to intervene and requested that this court stay
the production of the documents to which they had asserted
a privilege in the district court. We granted a temporary
stay and remanded the case to the district court for the
limited purpose of permitting the district court to enter
more extensive findings regarding those documents to
which the Does claim a privilege. The remand order di-
rected the district court to perform an in camera inspection
of the documents at issue and to enter specific findings con-
sidering the totality of the circumstances surrounding the
Does’ privilege claim.


C. The Limited Remand
  On this limited remand, the district court did not per-
form a comprehensive review of all the documents that
contained information identifying the Does, but instead re-
quested counsel to produce a subset for in camera inspec-
tion. Specifically, the court ordered counsel to produce all
confidentiality agreements, consulting agreements and en-
gagement letters entered into between BDO and the Does.
Upon reviewing this subset of documents, the court deter-
mined that the identities of at least 55 Does were not
subject to privilege under § 7525. It noted that many of the
confidentiality agreements establish that particular Does
engaged BDO’s services, in part, for the purpose of prepar-
ing income tax returns. In addition, several consulting
agreements contained a “No Warranty” provision, which
6                                        Nos. 02-3914, 02-3915

states that “BDO’s Services hereunder do not include . . .
any legal and/or tax opinions regarding any strategies that
may be implemented.” See United States v. BDO Seidman,
LLP, No. 02 C 4822, 

, at *3 (N.D. Ill. Feb. 5,
2003). This language, the court determined, suggests that
the relationship between BDO and the Does was not always
that of tax advisor-client and that, in such cases, their
communications would not be subject to the § 7525 privi-
lege. See 

Accordingly, the district court found that
133 of the documents it had reviewed established that
BDO’s communications with 55 Does had not been for the
purpose of providing tax advice, and were therefore not
privileged. Furthermore, the court concluded, 28 of the
documents were generated for the purpose of preparing tax
returns, another unprivileged category of communication.
See 

(citing United States v. Frederick, 

(7th
Cir. 1999)). Finally, with respect to 30 unidentified clients
who sought intervention, the court was unable to make
findings because no confidentiality agreements, consulting
agreements or engagement letters had been produced on
their behalf.


                                II
                        DISCUSSION
  On appeal, the Does submit that the district court erred
when it denied their motions to intervene on the ground
that the Does lacked a colorable claim of privilege under
§ 7525. Because the Does sought intervention as of right,
Fed. R. Civ. P. 24(a)(2), they had the burden of establishing
that: (1) their motions to intervene were timely; (2) they
possess an interest related to the subject matter of the en-
forcement action; (3) disposition of the action threatens to
impair that interest; and (4) the IRS and BDO fail to repre-
Nos. 02-3914, 02-3915                                          7

sent adequately their interest. See Vollmer v. Publishers Clear-
ing House, 

, 705 (7th Cir. 2001). To satisfy these
requirements, the Does must show that the “interest” as-
serted is a “direct, significant, legally protectable” one. Sec.
Ins. Co. of Hartford v. Schipporeit, 

, 1380 (7th Cir.
1995) (citation omitted). A colorable claim of privilege could
constitute a legally protectable interest sufficiently signifi-
cant to warrant intervention as of right, assuming that the
three remaining factors are also satisfied. See In re Grand Jury
Subpoena, 

, 570 (1st Cir. 2001). Failure to satisfy
any one of the four intervention factors is sufficient grounds
to deny the intervention. See 

. This
court reviews the foregoing factors de novo, with the
exception of the first factor—the timeliness of the interven-
tion—which this court reviews for abuse of discretion. 

Nissei Sangyo Am., Ltd. v. United States, 

,
438 (7th Cir. 1994).
  Before us, the only factor that the IRS disputes is whether
the Does satisfied their burden of demonstrating a legally
protectable interest in preventing the disclosure of the doc-
uments that would reveal their identities as individuals who
sought BDO’s advice regarding tax shelters.
  In the course of their submission, the Does advance sev-
eral additional arguments that challenge the district court’s
findings and conclusions on limited remand. For example,
they argue that the district court’s factual findings were
clearly erroneous because the court failed to consider the
totality of the circumstances surrounding each document.
They further argue that the district court erroneously con-
cluded that the asserted privilege would not have attached
even if the court properly found that BDO prepared tax re-
turns for some unidentified clients who discussed tax shel-
ters with BDO. Finally, the Does contend that there is no
basis to uphold the district court’s production order with
8                                      Nos. 02-3914, 02-3915

respect to the 30 unidentified clients for whom no findings
were made on the limited remand. These arguments all pre-
suppose that the district court erroneously concluded that
the § 7525 privilege cannot be asserted to prevent the dis-
closure of their identities. If that initial premise proves
wrong, there would be no reason to address any of these
arguments.
  We have jurisdiction to review the district court’s orders
because they definitively preclude the Does’ future partici-
pation in the IRS enforcement action against BDO. See
United States v. City of Milwaukee, 

, 528 (7th Cir.
1998); Williams v. Katz, 

, 191-92 (7th Cir. 1994).


A. A Colorable Claim of Privilege
   The primary issue before us is whether the district court
erred when it denied the Does’ motions to intervene because
it believed that they had failed to establish a colorable claim
of privilege under § 7525. Unless the Does can establish that
the § 7525 privilege can protect a taxpayer’s identity from
disclosure in the IRS enforcement action, the Does will not
prevail on appeal. Whether the scope of the § 7525 privilege
includes protection against the disclosure of client identity
is a question of law that this court reviews de novo. See In re
Subpoenaed Grand Jury Witness, 

, 512 (7th Cir.
1999).


    1. Regulatory Context
  We first consider the regulatory context in which the
Does’ claim of privilege arises. The Does sought to inter-
vene in proceedings involving the IRS investigation of BDO
for potential violations of the tax code, including the pro-
visions requiring organizers of tax shelters to register tax
Nos. 02-3914, 02-3915                                          9

shelters with the IRS, 26 U.S.C. § 6111, and organizers and
sellers of such shelters to keep lists of the investors, 26
U.S.C. § 6112. These provisions were enacted by Congress
as part of the Deficit Reduction Act of 1984, Pub. L. No. 98-
369, 98 Stat. 494 (1984), for the purpose of providing the IRS
with means to better monitor tax shelters, and, conse-
quently, to deter abusive tax shelters that can adversely
impact public revenues. See Elizabeth K. Lewicki, The Reg-
ulation of Tax Shelters and New Internal Revenue Code Section
469: A Complex and Unnecessary Addition to the War on
Abusive Tax Shelters, 19 Pac. L.J. 101, 115-16 (1987). Before
1984, no systematic information was available to assist the
IRS in identifying the shelters that should be investigated.
H.R. Conf. Rep. No. 98-861, at 977 (1984), reprinted in 1984
U.S.C.C.A.N. 1445, 1665. The IRS could audit individual
taxpayers, but such a process only randomly identified par-
ticipants in potentially abusive tax shelters. Lewicki, 19 Pac.
L.J. at 116. The statutory registration and list-keeping pro-
visions allow the IRS to identify more easily those transac-
tions that it deems to be abusive and “to identify quickly all
of the participants in related tax-shelter investments.” H.R.
Rep. No. 98-432, pt. 2, at 1351-52 (1984), reprinted in 1984
U.S.C.C.A.N. 697, 1004-05. These provisions also enable the
IRS to examine every purchaser of a given type of tax
shelter investment and to treat those taxpayers in a more
uniform manner. 

granting the IRS the broad power to issue
summonses to investigate violations of the tax code, see 26
U.S.C. § 7602, further provides the IRS with great latitude
to verify compliance with these tax shelter registration and
list-keeping provisions. See also Holifield v. United States, 

, 205 (7th Cir. 1990). Nevertheless, despite these
powerful investigative tools, the IRS’ investigatory power
is not absolute. If a taxpayer fails to comply with a sum-
10                                     Nos. 02-3914, 02-3915

mons, the IRS must apply to the district court to secure an
enforcement order. See 26 U.S.C. § 7604. Prior to enforcing
tax summonses, the court must scrutinize them to determine
whether they are made in good faith and seek information
relevant to a legitimate investigative purpose. See United
States v. Powell, 

, 57-58 (1964); Miller v. United
States, 

, 772 (7th Cir. 1998). Once the Govern-
ment makes a prima facie showing of good faith, the burden
shifts to the respondent to show that the enforcement of the
summons would constitute an abuse of process. See 2121
Arlington Heights Corp. v. IRS, 

, 1224 (7th Cir.
1997). “Summons enforcement proceedings are intended to
be summary in nature,” and it is left to the district court’s
discretion to determine whether a hearing is necessary. 

(citations omitted).
  The IRS’ broad power to investigate possible violations of
the tax laws is understood to be vital to the efficacy of the
federal tax system, “which seeks to assure that taxpayers
pay what Congress has mandated and to prevent dishonest
persons from escaping taxation thus shifting heavier bur-
dens to honest taxpayers.” United States v. Bisceglia, 

, 146 (1975). As the Supreme Court has noted, “the very
language of § 7602 reflects . . . a congressional policy choice
in favor of disclosure of all information relevant to a legiti-
mate IRS inquiry.” United States v. Arthur Young & Co., 

, 816 (1984). Because the IRS’ investigatory powers
are essential to the proper functioning of the tax system,
courts are reluctant to restrict the IRS’ summons power,
absent unambiguous direction from Congress. See 2121
Arlington 

(citations omitted).
Nevertheless, a court’s power to enforce a summons is not
absolute; it is subject to traditional privileges. Arthur Young
& 

.
Nos. 02-3914, 02-3915                                        11

  2. 26 U.S.C. § 7525
  Having described the general framework of this regula-
tory authority, we now turn to the specific context of the
Does’ claim. The Does seek to intervene to prevent the dis-
closure, through IRS summonses, of documents that the
Does contend are privileged. The Does’ privilege claim rests
entirely on § 7525, a statute enacted on July 22, 1998, to
provide a confidentiality privilege for communications be-
tween a taxpayer and a tax practitioner. This limited
privilege applies only to communications occurring after the
date of the statute’s enactment. See 

.
Section 7525, provides in pertinent part:
    With respect to tax advice, the same common law pro-
    tections of confidentiality which apply to a communica-
    tion between a taxpayer and an attorney shall also ap-
    ply to a communication between a taxpayer and any
    federally authorized tax practitioner to the extent the
    communication would be considered a privileged com-
    munication if it were between a taxpayer and an at-
    torney.
26 U.S.C. § 7525(a)(1). Thus the § 7525 privilege is no
broader than that of the attorney-client privilege, and
“[n]othing in [§ 7525] suggests that . . . nonlawyer practi-
tioners are entitled to privilege when they are doing other
than lawyers’ work.” 

. Because the
scope of the tax practitioner-client privilege depends on the
scope of the common law protections of confidential at-
torney-client communications, we must look to the body of
common law interpreting the attorney-client privilege to
interpret the § 7525 privilege.
  The attorney-client privilege is “one of the oldest recog-
nized privileges for confidential communications” known
to the common law. Swidler & Berlin v. United States, 524
12                                     Nos. 02-3914, 02-3915

U.S. 399, 403 (1998). The purpose of the privilege is to en-
courage full disclosure and to facilitate open communica-
tion between attorneys and their clients. 

“the privilege has the effect of withholding
relevant information,” courts construe the privilege to
apply only where necessary to achieve its purpose. Fisher v.
United States, 

, 403 (1976); see In re Grand Jury
Proceeding (Cherney), 

, 567 (7th Cir. 1990). The
mere assertion of a privilege is not enough; instead, a party
that seeks to invoke the attorney-client privilege has the
burden of establishing all of its essential elements. See In re
Grand Jury Proceedings (Thullen), 

, 571 (7th Cir.
2000); United States v. Evans, 

, 1461 (7th Cir.
1997).
   A party that seeks to assert a § 7525 privilege bears the
same burden. Among the essential elements of the attorney-
client privilege are the requirements that the communication
be made to the attorney in confidence, see 

, and that the confidences constitute information that
is not intended to be disclosed by the attorney, see United
States v. Weger, 

, 1154 (7th Cir. 1983) (“the
privilege protects only the client’s confidences, not things
which, at the time, are not intended to be held in the breast
of the lawyer”) (citation omitted); In re Grand Jury Proceed-
ings, 

, 1356 (4th Cir. 1984) (“[C]ourts have
consistently ‘refused to apply the privilege to information
that the client intends his attorney to impart to others . . .,’
or which the client intends shall be published or made
known to others.”) (collecting cases). Furthermore, the party
asserting a privilege must show that the attorney-client
communication was made for the purpose of obtaining legal
advice, or, more precisely in the case of the § 7525 privilege,
tax advice. See 

.
  The attorney-client privilege protects confidential commu-
nications made by a client to his lawyer, and so ordinarily
Nos. 02-3914, 02-3915                                      13

the identity of a client does not come within the scope of the
privilege. Tillotson v. Boughner, 

, 666 (7th Cir.
1965). However, over the years, a limited exception to this
general rule has developed; the identity of a client may be
privileged in the rare circumstance when so much of an
actual confidential communication has been disclosed al-
ready that merely identifying the client will effectively dis-
close that communication. See In re Subpoenaed Grand Jury

; 

; In re
Witnesses Before the Special March 1980 Grand Jury, 

, 494 (7th Cir. 1984); 

.
  In their discussion of this narrow exception, the parties
primarily focus on two cases in which we held that attor-
ney-client privilege could prevent the disclosure of a
client’s identity. In Tillotson, an unidentified taxpayer had
determined that he understated his tax liability on previ-
ously filed returns and retained an attorney to deliver a
cashier’s check in the amount of $215,499.95 to the 

. The IRS sought to enforce a summons it had
served on the attorney, demanding that he testify about his
client. The attorney asserted the attorney-client privilege
and refused to disclose his client’s identity. 

the invocation of the privilege because “under the peculiar
facts of this case, the attorney-client privilege includes,
within its scope, the identity of the client.” 

We
reasoned that the IRS had become aware of the substantive
content of the confidential communication between the un-
known taxpayer and his attorney—namely, the taxpayer’s
tax liability—the moment the cashier’s check was deliv-
ered. Because revealing the taxpayer’s identity would also
reveal the content of the confidential communication, the
privilege attached. 

Similarly, in Cherney, we held
that the privilege encompasses the identity of a client when
the Government knows that the unidentified client paid
14                                     Nos. 02-3914, 02-3915

fees for a criminal defendant out of concern about his own
involvement in the charged drug 

. In that case, we explained, the client’s identity was
privileged “because its disclosure would be tantamount to
revealing the premise of a confidential communication: the
very substantive reason that the client sought legal advice
in the first place.” 

words, “the privilege protects
an unknown client’s identity where its disclosure would
reveal a client’s motive for seeking legal advice.” Id.; see In
re Subpoenaed Grand Jury 

; 

.
  Relying on these cases, the Does submit that the IRS’
summonses set forth such detailed descriptions about sus-
pect types of tax shelters under investigation that any doc-
ument produced in response that also reveals a client’s
identity will inevitably reveal that client’s motivation for
seeking tax advice from BDO. The Does define their “mo-
tive” for retaining BDO’s services as the “desire to engage
in financial transactions which the government might later
decide to be questionable, or . . . ‘potentially abusive.’ ”
Appellants’ Br. at 16. Because a client’s “motive” for seeking
legal advice is considered a confidential communication, the
Does contend that the § 7525 privilege should protect
against the disclosure of their motive for seeking tax advice,
a motive that would be known if their identities are re-
vealed.
  The Does have not established that a confidential com-
munication will be disclosed if their identities are revealed
in response to the summonses. Disclosure of the identities
of the Does will disclose to the IRS that the Does partici-
pated in one of the 20 types of tax shelters described in its
summonses. It is less than clear, however, as to what mo-
tive, or other confidential communication of tax advice, can
be inferred from that information alone. Compared to the
Nos. 02-3914, 02-3915                                        15

situations in the Tillotson and Cherney cases, where the
Government already knew much about the substance of the
communications between the attorney and his unidentified
client, in this case the IRS knows relatively little about the
interactions between BDO and the Does, the nature of their
relationship, or the substance of their conversations. More-
over, the Does concede that the documents that BDO in-
tends to produce in response to the summonses are not sub-
ject to any other independent claim of privilege beyond the
Does’ assertion of privilege as to identity.
  More fundamentally, the Does’ participation in potentially
abusive tax shelters is information ordinarily subject to full
disclosure under the federal tax law. See 26 U.S.C §§ 6111,
6112. Congress has determined that tax shelters are subject
to special scrutiny, and anyone who organizes or sells an
interest in tax shelters is required, pursuant to I.R.C. § 6112,
to maintain a list identifying each person to whom such an
interest was sold. This list-keeping provision precludes the
Does from establishing an expectation of confidentiality in
their communications with BDO, an essential element of the
attorney-client privilege and, by extension, the § 7525
privilege. See 

. At the time that the
Does communicated their interest in participating in tax
shelters that BDO organized or sold, the Does should have
known that BDO was obligated to disclose the identity of
clients engaging in such financial transactions. Because the
Does cannot credibly argue that they expected that their
participation in such transactions would not be disclosed,
they cannot now establish that the documents responsive to
the summonses, which do not contain any tax advice, reveal
a confidential communication. 

(a
communication must be made in confidence to be privileged
under § 7525).
  BDO’s affirmative duty to disclose its clients’ participa-
tion in potentially abusive tax shelters renders the Does’
16                                     Nos. 02-3914, 02-3915

situation easily distinguishable from the limited circum-
stances in which we have determined that a client’s identity
was information subject to the attorney-client privilege. The
district court committed no error when it concluded that the
Does failed to establish a colorable claim of privilege under
§ 7525.


                        Conclusion
  Because the Does cannot demonstrate a colorable claim of
privilege, they have failed to establish a legally protectable
interest in preventing the disclosure of the documents
revealing their identities as individuals who participated in
tax shelters promoted by the BDO. For the reasons stated
above, the district court’s judgments denying the Does’ mo-
tions for intervention are affirmed.
                                                   AFFIRMED

A true Copy:
        Teste:

                          _____________________________
                           Clerk of the United States Court of
                             Appeals for the Seventh Circuit




                    USCA-02-C-0072—7-23-03