REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING
FIRM

To the Board of Trustees of MFS
Series Trust XIV and Shareholders of MFS Institutional
Money Market Portfolio:

In planning and performing our audit of the financial
statements of MFS Institutional Money Market
Portfolio (one of the series of MFS Series Trust XIV)
(the Fund)as of and forthe yearended August31,2018,
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
oversafeguarding securities,as a basis fordesigning
our auditing proceduresforthe purpose ofexpressing
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 Funds internal control overfinancialreporting.
Accordingly,we express no such opinion.

The management ofthe Fundis  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 fundsinternal 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.A funds 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
fund;(2) provide reasonable assurance that transactions
are recorded as necessary to permit
preparation of financial statements in accordance with
generally accepted accounting principles,
and that receipts and expenditures of the fund are
being made only in accordance with authorizations
of management of the fund and trustees of the trust;
and (3) provide reasonable assurance regarding
prevention or timely detection of unauthorized
acquisition, use, or disposition of a funds 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 becomeinadequate 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 operation, including controls
for safeguarding securities, that
we consider to be a material weakness,
as defined above, as of August31,2018.

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

DELOITTE & TOUCHE LLP

Boston, Massachusetts
October 16, 2018