Sec Form 4 Filing - Accel X LP @ Slack Technologies, Inc. - 2019-06-20

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Accel X LP 2. Issuer Name and Ticker or Trading Symbol Slack Technologies, Inc. [ WORK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 500 UNIVERSITY AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2019 (Street) PALO ALTO, CA94301 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A Common Stock 06/20/2019 S 6,725,250 D $ 38.5 10,420,830 D ( 1 ) Class A Common Stock 06/20/2019 S 896,700 D $ 40.76 ( 2 ) 9,524,130 D ( 1 ) Class A Common Stock 06/20/2019 J( 3 ) 8,967,000 D $ 0 557,130 D ( 1 ) Class A Common Stock 06/20/2019 S 504,750 D $ 38.5 782,123 I By Accel X Strategic Partners L.P. ( 4 ) Class A Common Stock 06/20/2019 S 67,300 D $ 40.76 ( 2 ) 714,823 I By Accel X Strategic Partners L.P. ( 4 ) Class A Common Stock 06/20/2019 J( 5 ) 673,000 D $ 0 41,823 I By Accel X Strategic Partners L.P. ( 4 ) Class A Common Stock 06/20/2019 S 270,000 D $ 38.5 418,373 I By Accel Investors 2009 L.L.C ( 6 ) Class A Common Stock 06/20/2019 S 36,000 D $ 40.76 ( 2 ) 382,373 I By Accel Investors 2009 L.L.C ( 6 ) Class A Common Stock 06/20/2019 J( 7 ) 360,000 D $ 0 22,373 I By Accel Investors 2009 L.L.C ( 6 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Accel X LP 500 UNIVERSITY AVENUE PALO ALTO, CA94301 X ACCEL X STRATEGIC PARTNERS LP 500 UNIVERSITY AVENUE PALO ALTO, CA94301 X Accel X Associates L.L.C. 500 UNIVERSITY AVENUE PALO ALTO, CA94301 X Accel Investors 2009 L.L.C. 500 UNIVERSITY AVE. PALO ALTO, CA94301 X Signatures /s/ TRACY L. SEDLOCK, ATTORNEY IN FACT 06/24/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares are held by Accel X L.P. Accel X Associates L.L.C. ("Accel X GP") is the general partner of each of Accel X L.P. and Accel X Strategic Partners L.P. (together, the "Accel X Entities"). Accel X GP has sole voting and dispositive power with regard to the shares held by the Accel X Entities. Accel X GP disclaims Section 16 beneficial ownership over the securities reported herein except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that such reporting person is the beneficial owner of such securities for Section 16 or any other purpose. ( 2 )The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $40.50 to $41.05. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. ( 3 )On June 20, 2019, Accel X L.P. distributed, for no consideration, 8,967,000 shares of Class A common stock of the Issuer (the "Accel X Shares") to its limited partners and to Accel X GP, the general partner of Accel X L.P., representing each such partner's pro rata interest in such Accel X Shares. On the same date, Accel X GP distributed, for no consideration, the Accel X Shares it received in the distribution by Accel X L.P. to its members, representing each such member's pro rata interest in such Accel X Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended. ( 4 )These shares are held by Accel X Strategic Partners L.P. Accel X GP disclaims Section 16 beneficial ownership over the securities reported herein except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that such reporting person is the beneficial owner of such securities for Section 16 or any other purpose. ( 5 )On June 20, 2019, Accel X Strategic Partners L.P. distributed, for no consideration, 673,000 shares of Class A common stock of the Issuer (the "Accel X Strategic Shares") to its limited partners and to Accel X GP, the general partner of Accel X Strategic Partners L.P., representing each such partner's pro rata interest in such Accel X Strategic Shares. On the same date, Accel X GP distributed, for no consideration, the Accel X Strategic Shares it received in the distribution by the Fund to its members, representing each such member's pro rata interest in such Accel X Strategic Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended. ( 6 )These shares are held by Accel Investors 2009 L.L.C. ( 7 )On June 20, 2019, Accel Investors 2009 L.L.C. distributed, for no consideration, 360,000 shares of Class A common stock of the Issuer (the "Accel 2009 Shares") to its members, representing each such member's pro rata interest in such Accel 2009 Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.

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