Is it permissible to use a complimentary travel voucher for a business trip and claim its value from the company, knowing that the company is obligated to purchase tickets for business trips?

The decisive factor lies in the agreed-upon conditions of the company with the employee, and what was contracted between them; Allah Almighty says: {O you who have believed, fulfill [all] contracts}, and the Prophet (peace and blessings be upon him) said: "Muslims are bound by their conditions." If the company covers the cost of the travel ticket for the employee without restricting him to a specific method, and the value of the ticket he possesses does not exceed the value covered by the company, then there appears to be no impediment to that. Otherwise, he must inform the company and obtain its approval.