AltMountain

Master Portfolio (A), L.P.

Boston, MA · CIK 1488800

Master Portfolio (A), L.P. is a hedge fund based in Boston, Massachusetts. According to its most recent Form D, filed Jan 21, 2026, the fund has sold $1,602,378,350 of interests to 228 investors since its first sale in Apr 2010. The minimum investment it accepts from an outside investor is $100,000. It relies on the Section 3(c)(7) exclusion, so investors generally must be qualified purchasers. The offering uses Rule 506(b), which does not permit general solicitation. Related persons named in the filing include Matt Libling; David Shushan; John Beil.

Performance

No verified returns have been reported for this fund. Hedge fund returns are not part of SEC filings; managers report them to AltMountain directly.

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Total raised
$1,602,378,350Cumulative sales reported on Form D
Investors
228
First sale
Apr 1, 2010
Minimum investment
$100,000
Who can invest
Qualified purchasersSection 3(c)(7): generally $5M+ in investments
Offering exemption
Rule 506(b)No general advertising
Key people and entities
Matt Libling; David Shushan; John Beil
Latest Form D
Jan 21, 2026

From SEC filings, not verified. This page republishes the fund's Form D as filed. It is not an offer, solicitation or recommendation, and AltMountain has not reviewed the fund. “Raised” is cumulative sales, not current assets or performance. Private funds are speculative, illiquid and generally limited to accredited investors or qualified purchasers. Full disclosures · Request a correction

Questions about Master Portfolio (A), L.P.

What is the minimum investment for Master Portfolio (A), L.P.?

According to its latest Form D, filed Jan 21, 2026, the minimum investment Master Portfolio (A), L.P. accepts from an outside investor is $100,000.

Who can invest in Master Portfolio (A), L.P.?

Master Portfolio (A), L.P. is generally open only to qualified purchasers (generally individuals with at least $5 million in investments), because it relies on Section 3(c)(7). It uses Rule 506(b), which does not allow general advertising.

How much has Master Portfolio (A), L.P. raised?

Master Portfolio (A), L.P. reports $1,602,378,350 sold from 228 investors on its Form D filed Jan 21, 2026. This is cumulative sales since the offering began, not current assets or performance.

Where is Master Portfolio (A), L.P. based?

Master Portfolio (A), L.P. is based in Boston, Massachusetts.

When did Master Portfolio (A), L.P. launch?

Master Portfolio (A), L.P. reports its first sale in Apr 2010.

Size compared with every hedge fund

Raised more than 87% of the 474 hedge funds based in Massachusetts, and more than 94% of all 10,307 that report sales.

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