4. Is there a ban on corporate donations to candidates?

Código Electoral de la República de Panamá
Artículo 230:
Quedan prohibidas las siguientes donaciones o aportes a partidos políticos, precandidatos y candidatos:
1. Los provenientes de personas jurídicas que no ejerzan actividades económicas dentro de la República de Panamá.
2. Las donaciones o los aportes anónimos, salvo los que se originen en colectas populares reglamentadas en este Código.
3. Las donaciones o los aportes que provengan de gobiernos, personas u organismos extranjeros. Se exceptúan las donaciones o los aportes de partidos políticos, asociaciones internacionales de partidos y fundaciones extranjeras que están vinculadas con partidos o fundaciones nacionales, siempre que dichas donaciones o aportes no sean para campañas electorales.
4. Los provenientes de empresas donde el Estado sea accionista.
Los provenientes de personas naturales o jurídicas, que de forma directa o como parte de un grupo económico, que, al momento de la donación, sean contratistas del Estado o concesionarios de servicios públicos.
6. Las provenientes de congregaciones religiosas de cualquier denominación u origen, sean nacionales o extranjeros.
7. Los de personas naturales o jurídicas condenadas con sentencia ejecutoriada, por delitos contra la administración pública, tráfico ilícito de drogas, minería ilegal, tala ilegal, trata de personas, lavado de activos o terrorismo. 
                                                                                                                 

Article 230:
The following donations or contributions to political parties, pre-candidates and candidates are prohibited: 
1. Those coming from juridical persons that do not exercise economic activities within the Republic of Panama.
2. Donations or anonymous contributions, except for those originating in popular collections regulated in this Code.
3. Donations or contributions from foreign governments, persons or organizations, foreign governments, persons or organizations. Exceptions are donations or contributions from political parties, international associations of parties and foundations that are linked to national parties or foundations, as long as such donations or contributions are not for electoral campaigns.
4. Those coming from companies where the State is a shareholder.
Those coming from natural or juridical persons, who directly or as part of an economic group, which, at the time of the donation, are contractors of the contractors of the State or concessionaires of public services.
6. Those coming from religious congregations of any denomination or origin, whether national or foreign.
7. Those of natural or juridical persons condemned with an enforceable sentence, for crimes against the public administration, illicit drug trafficking, illegal mining, illegal logging, human trafficking, money laundering or terrorism.

Unofficial English translation.

There are two exceptions 1. when that, at the time of the donation, the companies were contractors of the State or concessionaires of public services (art 230. 5) and when legal person were s convicted with an enforceable sentence, for crimes against public administration, illicit drug trafficking, illegal mining, illegal logging, human trafficking, money laundering or terrorism (art 230. 7).