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Monitor Institutional Holdings Changes

Institutional investors managing over $100M must disclose their equity holdings quarterly via SEC Form 13F. This tutorial shows how to retrieve those holdings and compare them across quarters to detect position changes.

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Prerequisites

  • An Omni Datastream API key (set as OMNI_DATASTREAM_API_KEY)
  • Basic familiarity with REST APIs
  • (Optional) Python 3.8+ or Node.js 18+ for SDK examples

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Step 1 — Retrieve current 13F holdings

Use /v1/owners/13f to pull the latest holdings for an institutional investor by their CIK number.

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curl

curl -H "x-api-key: $OMNI_DATASTREAM_API_KEY" \
  "https://api.secapi.ai/v1/owners/13f?cik=0001067983&limit=20"

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Python

from omni_datastream_py import OmniDatastreamClient

client = OmniDatastreamClient(api_key="your-api-key")

holdings = client.owners.thirteenf(cik="0001067983", limit=20)

for holding in holdings.data:
    print(f"{holding.issuer_name}: {holding.value:,} ({holding.shares:,} shares)")

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JavaScript

import { OmniDatastreamClient } from "@omni-datastream/sdk-js";

const client = new OmniDatastreamClient({
  apiKey: process.env.OMNI_DATASTREAM_API_KEY!,
});

const holdings = await client.owners.thirteenF({
  cik: "0001067983",
  limit: 20,
});

for (const holding of holdings.data) {
  console.log(
    `${holding.issuerName}: ${holding.value.toLocaleString()} (${holding.shares.toLocaleString()} shares)`
  );
}

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Expected output

APPLE INC: 84,248,000 (400,000,000 shares)
BANK OF AMER CORP: 41,071,000 (1,032,852,006 shares)
AMERICAN EXPRESS CO: 38,367,000 (151,610,700 shares)
COCA COLA CO: 25,440,000 (400,000,000 shares)

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Step 2 — Compare holdings across quarters

The /v1/owners/13f/compare endpoint shows what changed between two filing periods. This surfaces new positions, closed positions, and share count changes.

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curl

curl -H "x-api-key: $OMNI_DATASTREAM_API_KEY" \
  "https://api.secapi.ai/v1/owners/13f/compare?cik=0001067983&period_a=2024-Q3&period_b=2024-Q4"

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Python

diff = client.owners.thirteenf_compare(
    cik="0001067983",
    period_a="2024-Q3",
    period_b="2024-Q4",
)

for change in diff.data:
    direction = "+" if change.shares_change > 0 else ""
    print(f"{change.issuer_name}: {direction}{change.shares_change:,} shares ({change.change_type})")

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JavaScript

const diff = await client.owners.thirteenFCompare({
  cik: "0001067983",
  periodA: "2024-Q3",
  periodB: "2024-Q4",
});

for (const change of diff.data) {
  const direction = change.sharesChange > 0 ? "+" : "";
  console.log(
    `${change.issuerName}: ${direction}${change.sharesChange.toLocaleString()} shares (${change.changeType})`
  );
}

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Expected output

{
  "data": [
    {
      "issuer_name": "APPLE INC",
      "shares_previous": 400000000,
      "shares_current": 300000000,
      "shares_change": -100000000,
      "change_type": "reduced"
    },
    {
      "issuer_name": "SIRIUS XM HOLDINGS INC",
      "shares_previous": 0,
      "shares_current": 108752027,
      "shares_change": 108752027,
      "change_type": "new_position"
    }
  ]
}

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Step 3 — Build a quarterly monitoring workflow

Combine the two endpoints to build a script that runs after each 13F filing deadline (45 days after quarter end) and flags material changes.

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Python

MANAGERS = [
    {"name": "Berkshire Hathaway", "cik": "0001067983"},
    {"name": "Bridgewater Associates", "cik": "0001350694"},
]

THRESHOLD_PCT = 10  # flag changes over 10%

for manager in MANAGERS:
    diff = client.owners.thirteenf_compare(
        cik=manager["cik"],
        period_a="2024-Q3",
        period_b="2024-Q4",
    )

    significant = [
        c for c in diff.data
        if c.change_type in ("new_position", "closed")
        or abs(c.shares_change / max(c.shares_previous, 1)) > THRESHOLD_PCT / 100
    ]

    if significant:
        print(f"\n--- {manager['name']} ---")
        for c in significant:
            print(f"  {c.issuer_name}: {c.change_type} ({c.shares_change:+,} shares)")

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Next steps

  • Set up webhooks: Use the Filing Monitor tutorial to get notified when new 13F filings are published.
  • Cross-reference with insider trades: Combine 13F data with insider trading patterns for a complete ownership picture.
  • Track sector exposure: Aggregate holdings by sector to monitor allocation shifts.
See the Ownership Workflows guide for additional patterns.