No foreign equity is allowed in the practice of professions, although foreigners may practice the engineering profession subject to reciprocity.  According the Annex on Professions of the 11th Foreign Investment Negative List, the corporate practice is allowed for a few engineering activities only, excluding for instance civil engineering. However, even for those activities which investments through the corporate form is explicity admitted, the reciprocity requirement that is concurred in the case of such profession may not apply: cf. SEC-OGC Opinion No. 16-14, 23 May 2016, p. 3, related to the Foreign Participation in a Real Estate Brokerage Company ("[…] This means that the practice of profession by corporations should be done by 100% Filipino-owned corporations, as no foreign equity is allowed [...]). For the purposes of the OECD FDIRRI, the "no foreign equity" restriction is thus assume to apply to the entire sector.
"Only the investment areas and/or activities listed in the attached Eleventh Regular Foreign Investment Negative List shall be reserved for Philippine nationals, subject to the exceptions and conditions indicated therein.
[...]
LIST A: FOREIGN OWNERSHIP IS LIMITED BY MANDATE OF THE CONSTITUTION AND SPECIFIC LAWS
No Foreign Equity [...]
2. Practice of Professions² (Art. XII, Sec. 14 of the Constitution, Sec. 1 of R.A. No. 5181, Sec. 7[j] of R.A. No. 8981), including Radiologic and x-ray technology (R.A. No. 7431), Criminology (R.A. No. 6506), Law (Art. VIII, Section 5 of the Constitution; Rule 138, Sec. 2 of the Rules of Court of the Philippines), and Marine deck officers and marine engine officers (R.A. No. 10635), subject to the Annex on Professions attached herewith and forming an integral part of this document, indicating the professions where (a) foreigners are allowed to practice in the Philippines subject to reciprocity; and (b) where corporate practice is allowed. Foreigners may teach at higher education levels (R.A. No. 8292), provided the subject being taught is not a professional subject (i.e., included in a government board or bar examination). [²2 Section 1(b) of Professional Regulation Commission Resolution No. 2012-668 defines ‘practice of a profession” as an “activity/undertaking rendered by a registered and licensed professional or a holder of a Special Temporary Permit as defined in the scope of practice of a professional regulatory law.”]
[...]
ANNEX ON PROFESSIONS
A. Foreigners are allowed to practice the following professions in the Philippines provided that their home country allows Filipinos to be admitted to the practice of these professions: 
Accountancy (Sec. 34, R.A. No. 9298) 
Aeronautical engineering (Section 14, P.D. No. 1570)
Agricultural and biosystems engineering (Sections 15 and 31, R.A. No.10915) [...]
Architecture (Sections 13 and 27, R.A. No. 9266) 
Chemical engineering (Section 30, R.A. No. 9297 [...]
Civil engineering (Section 25, R.A. NO, 544, as amended) [...]
Electrical engineering (Section 38, R.A. No. 7920)
Electronics engineering (Sections 13 and 33. R.A. No. 9292) [...]
Geodetic engineering (Section26, R.A. No. 8560) [...]
Interior design (Sections 15 and 29 R.A. No. 10350)
Landscape architecture (Sections 13 and 29) R.A. No. 9053) [...]
Mechanical engineering (Section 39, R.A. No. 8495) [...]
Metallurgical engineering (Sections 17 and 34, R.A. No. 10688) [...]
Mining engineering (Sections 15, 16, and 28, R.A. No. 10698)
Naval architecture (Sections 13 and 31 R.A. No. 10698)
[...]
B. Corporate practice is allowed in the following professions, subject to the requirements and conditions under the pertinent professional regulatory law:
Aeronautical engineering (Section 28, P.D. No. 1570)
Agricultural and biosystems engineering (Section 29, R.A. No. 10915)
Architecture (Section 37, R.A. No. 9266) [...]
Electronics engineering (Section 28, R.A. No. 9292)
Environmental planning (Section 25, R.A. No. 10587) [...]
Interior design (Section 26, R.A. No 10350)
Landscape architecture (Section 26, R.A. No. 9053)
Naval Architecture (Section 30 [g], R.A. No. 10698) [...]
Sanitary engineering (Section 30, R.A. No. 1364)" (Eleventh Regular Foreign Investment Negative List (Executive Order No. 65 / 2018))
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"SECTION 14. The sustained development of a reservoir of national talents consisting of Filipino scientists, entrepreneurs, professionals, managers, high-level technical manpower and skilled workers and craftsmen in all fields shall be promoted by the State. The State shall encourage appropriate technology and regulate its transfer for the national benefit.
The practice of all professions in the Philippines shall be limited to Filipino citizens, save in cases prescribed by law.[...]" (Art XII, Sec 14 of the Constitution, Sec 1 of RA 5181, Sec 7.j of RA 8981)
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"The Ninth Regular Foreign Investment Negative List (FINL-9), pursuant to theConstitution and specific laws, provides, in List A, that no foreign equity is allowed for thepractice of professions, including real estate services, as such practice is limited to Filipinocitizens, save in cases prescribed by law. This means that the practice of profession bycorporations should be done only by 100% Filipino-owned corporations, as no foreignequity is allowed.
[...]
Based on the foregoing, we are of the view that no foreign participation is allowed incorporations, such as a real estate brokerage company, that will engage in the practice of realestate service.[...]" (SEC-OGC Opinion No. 16-14 Foreign Participation in a Real EstateBrokerage Company)

Eleventh Regular Foreign Investment Negative List (Executive Order No. 65 / 2018)
Art XII, Sec 14 of the Constitution, Sec 1 of RA 5181, Sec 7.j of RA 8981
SEC-OGC Opinion No. 16-14 of 23 May 2016 on Foreign Participation in a Real Estate Brokerage Company
[<a href="https://www.officialgazette.gov.ph/downloads/2018/10oct/20181029-EO-65-RRD.pdf">List</a>],[<a href="https://www.officialgazette.gov.ph/constitutions/1987-constitution/">Constitution</a>],[<a href="https://www.sec.gov.ph/wp-content/uploads/2019/12/2016OpinionNo16-14.pdf">Opinion</a>]