OSS · One Stop Systems, Inc.

The Reporting Person forfeited 19,675 shares of common stock upon conversion of an aggregate 50,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on June 6, 2023.

Includes 333,311 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person sold 8,000 shares of common stock upon conversion of an aggregate 21,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of sale. These restricted stock units were part of the grant to the Reporting Person on May 21, 2025.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 13,000 shares of common stock.

The Reporting Person sold 5,000 shares of common stock upon conversion of an aggregate 21,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of sale. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on May 28, 2025.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 37,000 shares of common stock.

The Reporting Person sold 8,000 shares of common stock upon conversion of an aggregate 21,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of sale. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on May 23, 2025.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 66,930 shares of common stock.

Represents 11,984 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 42,000 shares of common stock.

Represents 11,984 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 107,849 shares of common stock.

Represents 11,984 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 21,000 shares of common stock.

Represents 11,984 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 11,984 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 74,930 shares of common stock.

The Reporting Person forfeited 1,613 shares of common stock upon conversion of an aggregate 5,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on November 11, 2024.

Includes 127,762 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 6,650 shares of common stock upon conversion of an aggregate 21,908 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on July 1, 2024.

Includes 404,311 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On February 15, 2026 the Reporting Person transferred 4,263 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Shah-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 125,934 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 3,120 shares of common stock upon conversion of 7,383 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on July 1, 2024.

Includes 125,934 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

The Reporting Person forfeited 13,298 shares of common stock upon conversion of an aggregate 43,816 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on February 7, 2025.

Includes 426,219 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 6,546 shares of common stock upon conversion of 14,759 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on February 7, 2025.

Includes 133,317 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 55,239 restricted stock units granted to the Reporting Person under the Company's 2017 Equity Incentive Plan (the "Plan") in connection with the Reporting Person's ongoing service of the executive management team.

Includes 156,523 unvested restriced stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 34,313 restricted stock units granted to the Reporting Person under the Company's 2017 Equity Incentive Plan (the "Plan") in connection with the Reporting Person's ongoing service of the executive management team.

Includes 148,076 unvested restriced stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 7,799 shares of common stock upon conversion of an aggregate 23,761vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on February 7, 2025.

Includes 132,762 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 101,862 restricted stock units granted to the Reporting Person under the Company's 2017 Equity Incentive Plan (the "Plan") in connection with the Reporting Person's ongoing service of the executive management team.

Includes 470,035 unvested restriced stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On February 7, 2026 the Reporting Person transferred 8,213 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Shah-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 133,317 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

The Reporting Person forfeited 19,075 shares of common stock upon conversion of an aggregate 50,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on June 6, 2023.

Includes 368,173 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 3,215 shares of common stock upon conversion of an aggregate 10,000 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on November 11, 2024.

Includes 101,284 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

The Reporting Person forfeited 3,113 shares of common stock upon conversion of 7,384 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on March 20, 2023.

Includes 113,763 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On August 20, 2025 the Reporting Person transferred 4,271 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Shah-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 113,763 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 21,000 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 21,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 53,930 shares of common stock.

Represents 21,000 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 21,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 21,000 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 21,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions and 21,000 shares of common stock.

Represents 21,000 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), in connection with the Reporting Person's service as a director of the Issuer, which restricted stock units are subject to vesting conditions.

Includes 21,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

This Form 4/A amends the Form 4 filed on September 2, 2025, solely to correct a clerical error in the prior report, which incorrectly reflected the grant of 21,000 restricted stock units on May 21, 2025.

As a result of this update, the number of shares beneficially owned by the Reporting Person following such transaction has been correspondingly decreased by 21,000 shares. As of March 16, 2026, the Reporting Person beneficially owns 627,058 shares. This amendment does not reflect any change in beneficial ownership other than as described above.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

On February 20, 2025 the Reporting Person transferred 8,227 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Sha-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 121,147 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 7,006 shares of common stock upon conversion of 14,766 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on March 20, 2023

Includes 121,147 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

Represents 71,284 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended, in connection with the Reporting Person's continued service on the management team.

Consists of 111,284 unvested resticted stock units held by Reporting Person, all of which remain subject to certain vesting conditions.

Represents 44,279 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), which restricted stock units are subject to vesting conditions.

Consists of 135,913 restricted stock units held by the Reporting Person, all of which are subject to certain vesting conditions.

Represents 40,000 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended, in connection with the Reporting Person's appointment as Chief Financial Officer of the Issuer, which restricted stock units are subject to vesting conditions.

Consists of 40,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On September 23, 2024, the Reporting Person transferred 8,227 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Sha-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 91,634 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 5,961 shares of common stock upon conversion of 15,667 vested and outstanding restricted stock inits into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on March 20, 2023.

Includes 128,967 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 4,440 shares of common stock upon conversion of 12,667 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on March 20, 2023.

Includes 91,634 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On September 23, 2024, the Reporting Person transferred 8,227 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Sha-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

The Reporting Person forfeited 4,059 shares of common stock upon conversion of 10,667 vested and outstanding Restricted Stock Units into shares of common stock to cover tax withholdings, using the market price of the issuer's common stock at the time of forfeiture. These Restricted Stock Units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on February 7, 2022.

Includes 144,634 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On August 20, 2024, the Reporting Person transferred 6,062 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Sha-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

Includes 104,301 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The Reporting Person forfeited 3,271 shares of common stock upon conversion of 9,333 vested and outstanding restricted stock units into shares of common stock to cover tax withholdings, using the market price of the Issuer's common stock at the time of forfeiture. These restricted stock units were part of the grant reported in Table I of the Form 4 filed by the Reporting Person with the Securities and Exchange Commission on February 7, 2022.

Includes 104,301 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

On August 20, 2024, the Reporting Person transferred 6,062 shares of common stock to the James J. Ison Jr. & Sha-Marie A Ison TR UA 06 04 2020 James J. Ison Jr. & Sha-Marie A Ison Inter Vivos Revocable Trust (the "Trust"), of which the Reporting Person is trustee. The Reporting Person and members of his immediate family are the sole beneficiaries of the Trust.

These shares are owned directly by the Trust, and indirectly by James Ison as trustee of the Trust.

The shares are owned directly by Horton Capital Partners Fund, LP ("HCPF"). The Reporting Person, solely by virtue of his position as the managing member of Horton Capital Management, LLC ("HCM"), which serves as the investment manager of HCPF, and as the managing member of Horton Capital Partners, LLC, which serves as the general partner of HCPF, may be deemed to beneficially own the shares held by HCPF for purposes of Section 16. The Reporting Person expressly disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

The shares are owned directly by Horton Capital Partners Fund, LP ("HCPF"). The Reporting Person, solely by virtue of his position as the managing member of Horton Capital Management, LLC ("HCM"), which serves as the investment manager of HCPF, and as the managing member of Horton Capital Partners, LLC, which serves as the general partner of HCPF, may be deemed to beneficially own the shares held by HCPF for purposes of Section 16. The Reporting Person expressly disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.

Includes 21,000 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.

The option is fully vested.

Represents 44,300 restricted stock units granted to the Reporting Person under the Issuer's 2017 Equity Incentive Plan, as amended (the "Plan"), which restricted stock units are subject to vesting conditions.

Includes 113,634 unvested restricted stock units held by the Reporting Person, all of which remain subject to certain vesting conditions.