Form 4 transaction codes explained
Every row on a Form 4 carries a one-letter transaction code describing what kind of event it is. Most insider-trading tools only handle a handful of the most common codes (P, S, A, M) and default everything else to "other." InsiderTradingRadar maps all 20 codes that appear on real Form 4 filings -- an unmapped code silently falling through to a generic bucket is exactly the kind of gap that turns a correctness product into a guessing one.
The full code table
| Code | Meaning | Discretionary signal? |
|---|---|---|
| P | Open market or private purchase | Yes -- open market buy |
| S | Open market or private sale | Yes -- open market sale (may still be a scheduled 10b5-1 plan trade, see below) |
| A | Grant or award (Rule 16b-3(d)) | No -- compensation |
| M | Exercise/conversion exempted under Rule 16b-3 | No -- mechanical |
| G | Bona fide gift | No |
| F | Shares withheld to cover taxes on vesting (Rule 16b-3) | No -- mechanical |
| C | Conversion of a derivative security | No |
| X | Exercise of an in-the-money or at-the-money derivative | No -- mechanical |
| D | Disposition to the issuer (Rule 16b-3(e)) | No |
| J | Other -- footnote required to interpret | Depends on footnote text |
| U | Disposition pursuant to a tender offer | No |
| O | Exercise of an out-of-the-money derivative | No -- mechanical |
| E | Expiration of a short derivative position | No |
| H | Expiration or cancellation of a long derivative position | No |
| I | Discretionary transaction (Rule 16b-3(f)) | Depends on footnote text |
| K | Equity swap or similar instrument | Depends on footnote text |
| L | Small acquisition (Rule 16a-6) | Depends on footnote text |
| V | Voluntarily reported early | Depends on footnote text |
| W | Acquisition/disposition by will or laws of descent | No |
| Z | Deposit into or withdrawal from a voting trust | Depends on footnote text |
Why "S" (sale) needs a second filter
A large share of open-market sale ("S") transactions are pre-scheduled Rule 10b5-1 plan sales -- decided months in advance as part of an automatic trading plan, not a real-time decision reflecting the insider's current view of the stock. Form 4 carries a checkbox for this. Counting every "S" code as a bearish signal without checking it substantially overstates real insider selling pressure. InsiderTradingRadar surfaces the 10b5-1 flag and excludes it from alerts by default.
What "requires review" means
Codes like J, I, K, L, V, and Z depend on footnote text that's unstructured free text written by different filing agents and law firms -- there's no clean, reliable way to auto-interpret every footnote's meaning. InsiderTradingRadar stores and surfaces the raw footnote text rather than guessing at it, so you can judge these cases yourself instead of trusting a silent misclassification.