The statutory authority for adjustment of status is INA § 245(a), which permits an applicant in the United States to adjust to lawful permanent resident status if (i) the applicant was inspected and admitted or paroled into the United States, (ii) an immigrant visa is immediately available at the time the application is filed, and (iii) the applicant is otherwise admissible. Concurrent filing is permitted by 8 C.F.R. § 245.2(a)(2)(i)(B), which allows an I-485 to be filed simultaneously with an I-140 immigrant petition where the priority date is current at the time of filing.
For EB-1A petitioners, the immigrant petition is the I-140 filed under 8 C.F.R. § 204.5(h). EB-1 categories have historically had more favorable visa bulletin movement than EB-2 and EB-3, and for many countries of chargeability EB-1 has remained current for extended periods. Whether concurrent filing is permitted in any specific case turns on the country of chargeability and the Visa Bulletin in the month of filing — petitioners from countries with retrogressed EB-1 cut-off dates cannot file concurrently and must wait for the priority date to become current.
Filing the I-485 unlocks two ancillary benefits. An applicant with a pending I-485 may apply for an Employment Authorization Document under 8 C.F.R. § 274a.12(c)(9), commonly referred to as an "(c)(9) EAD," which authorizes any employment in the United States while the I-485 is pending. The same applicant may apply for Advance Parole on Form I-131 under 8 C.F.R. § 212.5(f) (pursuant to INA § 212(d)(5)), which allows international travel without abandoning the pending I-485 under 8 C.F.R. § 245.2(a)(4)(ii)(B). Most petitioners file the I-765 (EAD) and I-131 (AP) applications together with the I-140 and I-485 as a single packet; current USCIS practice combines the EAD and AP into a single travel-and-work document in many cases.
Section 245(a) imposes admissibility and status requirements that some EB-1A petitioners cannot satisfy. INA § 245(c) bars adjustment for applicants who, with limited exceptions, have engaged in unauthorized employment, have failed to maintain lawful status continuously since entry, or are otherwise ineligible. INA § 245(k) provides a safe harbor for employment-based applicants that excuses up to 180 days of unauthorized employment or status violations since the most recent lawful admission. The 245(k) calculation is non-trivial and turns on the timing of any status gaps relative to the filing of the I-485.