AOS / EOS / COS — three easily confused terms
Adjustment of Status (I-485), Extension of Stay, and Change of Status: the core differences, gray zones (authorized stay while I-485 is pending, bridging applications, 180-day portability), and how they map to Form I-129 / I-539 / I-485.
Last reviewed: 2026-07-06
This page maps the three forms and legal tracks. AC21 portability, UP tolling while I-485 is pending, and cap-gap are frequent gray zones.
AOS (I-485) adjusts to LPR in the US. EOS (I-129 / I-539) extends the I-94 in the same classification. COS (I-129 / I-539) changes classification. Each affects status and authorized stay differently; the pending-I-485 window is the biggest gray zone.
| Abbr. | Full name / Form | What it does | Typical scenario |
|---|---|---|---|
| AOS | Adjustment of Status · I-485 | Adjusts to LPR inside the US. | EB / FB when the priority date is current. |
| EOS | Extension of Stay · I-129 / I-539 | Extends I-94 in the same classification. | H-1B extension within 6 yrs; B-2 6→12 months. |
| COS | Change of Status · I-129 / I-539 | Swap one nonimmigrant classification for another without leaving the US. | F-1 → H-1B (cap-gap); B-2 → F-1; L-2 → H-4. |
Key gray zones while I-485 is pending
- Pending I-485 is generally authorized stay even if the underlying I-94 has expired — no UP accrues, though strictly you no longer hold a nonimmigrant status.
- Denial can immediately end authorized stay; whether to appeal, refile, or depart is case-specific.
- Bridging applications (I-539 to keep e.g. B-2 alive) are a common hedge against long backlogs or denials.
- AC21 §106(c) portability: once I-140 is approved and I-485 pending >180 days, switch to same-or-similar occupation with a supplement J.
- Working on EAD or traveling on AP does not disturb the pending status; AP travel is not a §212(a)(9)(B) departure (Arrabally 2012).
Which form?
- I-129: H/L/O/P/E/TN and other employment principals — initial / EOS / COS.
- I-539: B/F/M/J and dependents (H-4/L-2/O-3/TD) — EOS / COS.
- I-485: adjust to LPR; typically filed with I-131 (AP) and I-765 (EAD).
Legal terminology quick reference
Split by axis + events; click a term to jump to the matching definition section on this site.
| 中文 | English | Axis / Category | One-liner |
|---|---|---|---|
| 合法身份 | lawful status / legal status | status axis | Complying with classification conditions; a subset of authorized stay. |
| 失去身份 | out of status | status axis | Violation of classification conditions; ≠ automatic UP accrual. |
| 授权停留期 | period of stay authorized | presence axis | The §212(a)(9)(B) primary anchor; UP does not accrue during this period. |
| 非法滞留 (UP) | unlawful presence | presence axis | Accrues in real time in-country; settles into a bar upon departure. |
| 超期停留 | overstay | event | Past the I-94 date; triggers §222(g) visa voidance. |
| 离境 | departure | event | The event that settles accrued UP into a 3 / 10-year bar. |
| §222(g) 签证作废 | §222(g) visa voidance | event consequence | Triggered by overstay; decoupled from UP / bar mechanics. |
| 3 / 10 年禁令 | 3 / 10-year bar | settlement outcome | INA §212(a)(9)(B); single continuous UP; activates on departure. |
| 永久禁令 | permanent bar | settlement outcome | INA §212(a)(9)(C); aggregate UP > 1 year + later reentry/attempt without admission. |
This site provides general information only.
Frequently asked (FAQ)
Are AOS and COS the same?
No. AOS (I-485) adjusts you to LPR (green card) inside the US. COS (I-129 or I-539) swaps one nonimmigrant classification for another. Different forms, different legal tracks, different outcomes.
EOS vs COS?
EOS extends the I-94 within the same nonimmigrant classification. COS changes classification. Employment cases usually combine both on I-129; B/F/J/M and dependents use I-539.
What is my status while I-485 is pending?
Not strictly a nonimmigrant status, but it counts as authorized stay — so no UP accrues. If the I-485 is denied, the prior nonimmigrant status does not automatically snap back.
What is a bridging application?
Filing I-539 (or I-129) to keep an underlying nonimmigrant status (e.g., H-1B, B-2) alive while I-485 is pending — a hedge against I-485 denial. Whether it is needed depends on AC21 portability, EAD status, and travel needs.
What is AC21 §106(c) 180-day portability?
Once I-140 is approved and I-485 has been pending ≥180 days, you may switch to a same-or-similar occupation without a new PERM/I-140; the new employer files a supplement J.
F-1 student wants to stay — EOS or COS?
Continuing to study = extend I-20 via SEVIS/DSO (not I-539). Switching to H-1B = COS or cap-gap. Switching to B-2 short stay = I-539 COS.
What happens if COS is denied?
If your original I-94 is still valid, you remain in the prior status. If it already expired, unauthorized stay may be found retroactively — consult counsel about §222(g) and UP accrual.
When do I use I-129 vs I-539?
I-129 is for employment-based principals (H/L/O/E/P/TN...) initial, EOS, and COS. I-539 is for dependents (H-4/L-2) and B/F/M/J EOS/COS and other non-employment categories.
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This site provides general information only. It is not legal advice and does not create an attorney–client relationship. Consult a qualified U.S. immigration attorney about your case. i-94.org is independent and is not affiliated with DHS, CBP, USCIS, ICE, or any government agency. Actual I-94 lookup and reminder tools are provided by i94.io.