SEC Form SC 13G/A filed by MarketAxess Holdings Inc. (Amendment)

[X]

Rule 13d-1(b)

[  ]

Rule 13d-1(c)

[  ]

Rule 13d-1(d)

CUSIP No. 57060D108

1.

Names of Reporting Persons.
Guardian Capital LP

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

......[ ]

(b)

......[X]

3.

SEC Use Only ..........................................................................

4.

Citizenship or Place of Organization

Ontario, Canada

Number of
Shares
Beneficially
Owned by
Each Reporting
Person With

5.

Sole Voting Power 0.............................................................................................................

6.

Shared Voting Power

1,244,556

7.

Sole Dispositive Power

0

8.

Shared Dispositive Power

1,882,832

9.

Aggregate Amount Beneficially Owned by Each Reporting Person

1,882,832

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions).................................

11.

Percent of Class Represented by Amount in Row (9) 5.0%.....................................................................

12.

Type of Reporting Person (See Instructions)

IA

CUSIP No. 57060D108

1.

Names of Reporting Persons.

GuardCap Asset Management Limited

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

........[  ]

(b)

........[X]

3.

SEC Use Only .............................................................................

4.

Citizenship or Place of Organization

United Kingdom

Number of
Shares
Beneficially
Owned by
Each Reporting
Person With

5.

Sole Voting Power

0...................................................

6.

Shared Voting Power

1,222,801

7.

Sole Dispositive Power

0

8.

Shared Dispositive Power

1,861,077

9.

Aggregate Amount Beneficially Owned by Each Reporting Person

1,861,077

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions).................................

11.

Percent of Class Represented by Amount in Row (9) 4.9%....................................................................

12.

Item 1.

(a)

Name of Issuer
MarketAxess Holdings Inc. (the "Issuer")

(b)

Address of Issuer's Principal Executive Offices
55 Hudson Yards Floor 15, New York NY 10001

Item 2.

(a)

Name of Person Filing

This Statement is being filed on behalf of each of the following persons (each, a "Reporting Person" and collectively, the "Reporting Persons"):

(i) Guardian Capital, LP ("Guardian Capital"); and

(ii) GuardCap Asset Management Limited ("GuardCap").

Each Reporting Person declares that neither the filing of this Statement nor anything herein shall be construed as an admission that such person is, for the purposes of Section 13(d) or 13(g) of the Act or any other purpose, (i) acting (or has agreed or is agreeing to act) with any other person as a partnership, limited partnership, syndicate, or other group for the purpose of acquiring, holding, or disposing of securities of the Issuer or otherwise with respect to the Issuer or any securities of the Issuer or (ii) a member of any syndicate or group with respect to the Issuer or any securities of the Issuer.

(b)

Address of Principal Business Office or, if none, Residence

(i) The address of the principal business office of each Guardian Capital is Commerce Court West, Suite 2700, P.O. Box 201, Toronto, Ontario, Canada M5L 1E8

(ii) The address of the principal business office of each GuardCap is 6th Floor, 11 Charles II Street, St James's, London United Kingdom SW1Y 4NS

(c)

Citizenship
(i) Guardian Capital is an Ontario (Canada) Limited Partnership
(ii) GuardCap is a United Kingdom limited liability company

(d)

Title of Class of Securities
Common Stock, par value $0.003

(e)

CUSIP Number
57060D108

Item 3.

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

[  ]

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b)

[  ]

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

[  ]

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d)

[  ]

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

(e)

[X]

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

[  ]

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

[  ]

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

[  ]

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

[  ]

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

[  ]

Group, in accordance with §240.13d-1(b)(1)(ii)(J).

(a)

Amount beneficially owned:
Guardian Capital: 1,882,832
GuardCap: 1,861,077

(b)

Percent of class:
Guardian Capital: 5.0%
GuardCap: 4.9%

(c)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote
Guardian Capital LP: -0-
GuardCap: -0-

(ii)

Shared power to vote or to direct the vote
Guardian Capital LP: 1,244,556
GuardCap: 1,222,801

(iii)

Sole power to dispose or to direct the disposition of
Guardian Capital LP: -0-
GuardCap: -0-

(iv)

Shared power to dispose or to direct the disposition of
Guardian Capital LP: 1,882,832
GuardCap: 1,861,077

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

Not applicable.

Item 8.

Identification and Classification of Members of the Group

Not applicable.

Item 9.

Notice of Dissolution of Group

Not applicable.

Item 10.

Certification

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

GUARDIAN CAPITAL LP

/s/ Richard Britnell

Chief Compliance Officer

GUARDCAP ASSET MANAGEMENT LIMITED

/s/ Arieta Koshutova