X0306 4 2022-03-04 1 0001549922 Summit Midstream Partners, LP SMLP 0001761288 Stratton Marc David C/O SUMMIT MIDSTREAM PARTNERS, LP 910 LOUISIANA STREET, SUITE 4200 HOUSTON TX 77002 0 1 0 0 See remarks below. Common Units 2022-03-04 4 M 0 46659 A 46659 D Common Units 2022-03-04 4 F 0 394 15.58 D 46265 D Common Units 2022-03-04 4 F 0 1004 15.58 D 45261 D Common Units 2022-03-04 4 F 0 7639 15.58 D 37622 D Common Units 2022-03-04 4 F 0 11313 15.58 D 26309 D Phantom Units 2022-03-04 4 M 0 1306 0.00 D Common Units 1306 0 D Phantom Units 2022-03-04 4 M 0 3333 0.00 D Common Units 3333 0 D Phantom Units 2022-03-04 4 M 0 16937 0.00 D Common Units 16937 0 D Phantom Units 2022-03-04 4 M 0 25083 0.00 D Common Units 25083 0 D Each phantom unit is the economic equivalent of one common unit. On November 9, 2020, the Issuer effected a 1-for-15 reverse unit split (the "Reverse Unit Split"). Pursuant to the Reverse Unit Split, common unitholders received one common unit for every 15 common units owned at the close of business on November 9, 2020. All fractional units created by the Reverse Unit Split were rounded to the nearest whole unit. The common units began trading on a split-adjusted basis on November 10, 2020. After giving effect to the Reverse Unit Split, the number of issued and outstanding common units decreased to 3,774,992. Common Units being withheld to pay tax liability. The phantom units awarded on March 15, 2019 vested on March 4, 2022 according to the the Separation and General Release Agreement effective as of February 4, 2022. The Reporting Person received Distribution Equivalent Rights ("DERs") for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The phantom units and associated DERs do not expire. The phantom units are settled upon vesting in common units (on a one-for-one basis) or in cash, at the discretion of the Issuer. Total excludes phantom units from other tranches with different vesting and expiration dates. The phantom units awarded on November 15, 2019 vested on March 4, 2022 according to the the Separation and General Release Agreement effective as of February 4, 2022. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The phantom units awarded on March 23, 2020 with a Reference Date of March 15, 2020 vested on March 4, 2022 according to the the Separation and General Release Agreement effective as of February 4, 2022. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The phantom units awarded on February 17, 2021 with a Reference Date of March 15, 2021 vested on March 4, 2022 according to the the Separation and General Release Agreement effective as of February 4, 2022. The Reporting Person received DERs for each phantom unit, providing for payment on the vesting date of a lump sum of cash equal to the accrued distributions from and after the grant date of the phantom units. The Reporting Person is Executive Vice President and Chief Financial Officer of Summit Midstream GP, LLC, the general partner of the Issuer (the "General Partner"). The Issuer is managed by the directors and executive officers of the General Partner. /s/ James D. Johnston, Attorney-in-Fact for Marc D. Stratton 2022-03-08