Report of Independent Registered Public Accounting Firm

To the Shareholders and Board of Trustees of
Pioneer Bond Fund:

In planning and performing our audit of the financial statements of
Pioneer Bond Fund (the "Fund") as of and for the year ended June 30,
2021, in accordance with the standards of the Public Company
Accounting Oversight Board (United States) (PCAOB), we considered
the Fund's internal control over financial reporting, including
controls over safeguarding securities, as a basis for designing our
auditing procedures for the purpose of expressing our opinion on the
financial statements and to comply with the requirements of Form
N-CEN, but not for the purpose of expressing an opinion on the
effectiveness of the Fund's internal control over financial
reporting.  Accordingly, we express no such opinion.

The management of the Fund is responsible for establishing and
maintaining effective internal control over financial reporting. In
fulfilling this responsibility, estimates and judgments by management
are required to assess the expected benefits and related costs of
controls. A company's internal control over financial reporting is a
process designed to provide reasonable assurance regarding the
reliability of financial reporting and the preparation of financial
statements for external purposes in accordance with U.S. generally
accepted accounting principles. A company's internal control over
financial reporting includes those policies and procedures that
(1) pertain to the maintenance of records that, in reasonable
detail, accurately and fairly reflect the transactions and
dispositions of the assets of the company; (2) provide reasonable
assurance that transactions are recorded as necessary to permit
preparation of financial statements in accordance with U.S. generally
accepted accounting principles, and that receipts and expenditures of
the company are being made only in accordance with authorizations of
management and directors of the company; and (3) provide reasonable
assurance regarding prevention or timely detection of unauthorized
acquisition, use or disposition of a company's assets that could have
a material effect on the financial statements.

Because of its inherent limitations, internal control over financial
reporting may not prevent or detect misstatements. Also, projections
of any evaluation of effectiveness to future periods are subject to
the risk that controls may become inadequate because of changes in
conditions, or that the degree of compliance with the policies or
procedures may deteriorate.

A deficiency in internal control over financial reporting exists when
the design or operation of a control does not allow management or
employees, in the normal course of performing their assigned
functions, to prevent or detect misstatements on a timely basis.
A material weakness is a deficiency, or a combination of
deficiencies, in internal control over financial reporting, such that
there is a reasonable possibility that a material misstatement of the
company's annual or interim financial statements will not be
prevented or detected on a timely basis.

Our consideration of the Fund's internal control over financial
reporting was for the limited purpose described in the first
paragraph and would not necessarily disclose all deficiencies in
internal control that might be material weaknesses under standards
established by the PCAOB. However, we noted no deficiencies in the
Fund's internal control over financial reporting and its operation,
including controls over safeguarding securities that we consider to
be a material weakness as defined above as of June 30, 2021.

This report is intended solely for the information and use of
management and the Board of Trustees of Pioneer Bond Fund, and the
Securities and Exchange Commission and is not intended to be and
should not be used by anyone other than these specified parties.


/s/ ERNST& YOUNG LLP


Boston, Massachusetts
August 26, 2021