KPMG LLP
Two Financial Center 60
South Street
Boston, MA 02111





Report of Independent Registered Public Accounting Firm


The Board of Trustees and
Shareholders
Putnam Mortgage Securities
Fund:

In planning and performing our audit of the financial statements of
Putnam Mortgage Securities Fund (formerly U.S. Government income Trust)
(the Fund), as of and for the year ended September 30, 2018, in
accordance with the standards of the Public Company Accounting
Oversight Board (United States), we considered the Funds 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 NCEN, but not for the purpose of
expressing an opinion on the effectiveness of the Funds internal
control over financial reporting.  Accordingly, we express no such
opinion.

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 companys 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 generally accepted
accounting principles (GAAP). A companys 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 GAAP, and that receipts and
expenditures of the company are being made only in accordance with
authorizations of management and trustees of the company; and (3)
provide reasonable assurance regarding prevention or timely detection
of unauthorized acquisition, use or disposition of the companys 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 a funds annual
or interim financial statements will not be prevented or detected on a
timely basis.

Our consideration of the Funds 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
Public Company Accounting Oversight Board (United States). However, we
noted no deficiencies in the Funds internal control over financial
reporting and its operations, including controls over safeguarding
securities that we consider to be a material weakness defined above as
of September 30, 2018.

This report is intended solely for the information and use of
management and the Board of Trustees of Putnam Mortgage Securities 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.









Boston, Massachusetts
November 6, 2018




































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