Assalaamu alaykum. Can I supply lunch to banks and audit firms in return of payment?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

There is no apparent religious impediment to supplying meals to banks and audit firms, as this does not involve intentional or direct cooperation in committing a sin, so the basic principle applies to it, which is permissibility. The majority of the scholars held that the basic principle is that all transactions and contracts are permissible unless proven otherwise.

The Hanbali scholar Al-Haafith Ibn Rajab wrote, "Some (scholars) cited the consensus of scholars in this regard." [Jaamiʻ Al-ʻUloom wa Al-Hikam]

The subject of cooperation and what is permissible or impermissible thereof was extensively researched and discussed by the members of the Assembly of Muslim Jurists of America (AMJA) in its fifth round held in Bahrain in 1428 AH (2007 AD). They reached the following conclusion:

Cooperation in committing sin can be divided into four categories:

1- Direct, intentional help.

2- Direct but unintentional help.

3- Indirect but intentional help.

4- Indirect, unintentional help.

The AMJA's resolution ruled that the first three categories are impermissible while the fourth, namely the indirect and unintentional help, is permissible.

For more benefit, please refer to fatwa 321916.

Allah knows best.