What is the ruling for delaying work tasks and assignments until after official work hours to qualify for overtime compensation? In my workplace, I noticed that some colleagues deliberately postpone some tasks without any valid reason other than to qualify for extra compensation through overtime.

An employee is required to complete the assignments and tasks assigned to him in accordance with the contract concluded between him and the employer. It is impermissible in Islam to deliberately delay some work tasks beyond working hours without the approval of the relevant authorities. This conduct constitutes deception, breach of trust, as well as wrongfully acquired profit. Allah Almighty says, "O you who have believed, do not consume one another's wealth unjustly but only [in lawful] business by mutual consent" (Quran, 4:29).

Islamic advice on working and generating a lawful income
Islam places a strong emphasis on diligent work and the pursuit of a lawful income, enabling Muslims to contribute to their society and ensure a decent life for themselves and their families. Allah the Almighty says:
“And others travel throughout the land seeking of the bounty of Allah” (Quran, 73: 20). The Prophet (peace and blessings be upon him) also said, “No one eats better food than that which he eats out of the work of his own hand. Indeed, the Prophet of Allah, Dawood (peace be upon him), would eat from the earnings of his labor” (Bukhari).

Islam also demands sincerity and perfection in one's work as well as to safeguard every trust; Allah says, "Do good; indeed, Allah loves the doers of good" (Quran, 2:195).
Allah Almighty praises and describes his believing servants as, “Those who faithfully observe their trusts and their covenants” (Quran, 23:8). Therefore, the employees who perform their work duties effectively are rewarded for their sincerity, dedication and diligence, which is the path to Allah Almighty’s love. It is for this reason that the Messenger of Allah (peace and blessings be upon him) said, “Indeed, Allah Almighty loves when a person undertakes a job, to perform it with a commitment to excellence” (Al-Tabarani and al-Bayhaqi).

The Islamic stance on deferring work tasks to put in overtime
According to Islamic law, the relationship between an employer and an employee is classified as a lease contract (ijara), applicable to both public and private employment. In such a relationship, the employee performs designated duties for the other party within a specific timeframe in exchange for a predetermined renumeration. This relationship is regulated by the contract drawn up between both parties and the employment and labor law. Both parties are obligated to respect the provisions of the contract for Allah commands, “O you who have believed, fulfill [all] contracts.” (Quran, 5: 1). The Prophet (peace and blessings be upon him) also emphasized the importance of fulfilling contractual obligations when he said, “Muslims are bound by their conditions, except for a condition that forbids what is lawful or makes lawful what is forbidden” (At-Tirmidhi).

In Islamic law, the unjustified delay of assigned tasks during official work hours is prohibited, as it constitutes a breach of trust, which is considered a major sin and one of the characteristics of a hypocrite. The Prophet (peace and blessings be upon him) said, “The characteristics of a hypocrite are three: when he speaks, he lies; when he makes a promise, he breaks it; and when he is entrusted with something, he betrays that trust” (Bukhari and Muslim).

Furthermore, delaying and decelerating work commitments beyond the official work hours to secure double earnings is considered unlawful consumption of wealth. This is because the employee has squandered the official working hours without fulfilling their responsibilities and without a valid reason. Allah Almighty prohibits unlawful consumption of wealth by saying, “O you who have believed, do not consume one another's wealth unjustly but only [in lawful] business by mutual consent” (Quran, 4:29).
Additional Considerations regarding Public Funds
In addition to the above, the preservation of wealth, public or private, is one of the universal objectives that Islamic law seeks to protect. There is no doubt that such a transgression is more heinous and the sin greater when willful neglect involves public funds. This is because the harm does not affect a single individual, but the entire society. This is the reason why the Prophet (peace and blessings be upon him) augmented the prohibition of stealing, wasting, or exploiting public funds. He moreover entrusted its preservation to every member of the society because it is a collective ownership among all members of the society.  The Prophet (peace and blessings be upon him) said, "There are some who exploit public funds without a legitimate right; for them, there awaits Hellfire on the Day of Resurrection” (Bukhari). Allah Almighty also condemns the misuse of entrusted property with the words, “Whoever misappropriates [an entrusted item or public wealth] will bring forth what they misappropriated on the Day of Resurrection” (Quran, 3: 161).
The ruling
Based on the above, it is impermissible to defer any assigned work during official working hours to receive overtime compensation. This is a form of deception, breach of trust, and unjust consumption of wealth. Employees must fulfill their contractual obligations and refrain from taking any actions that jeopordize their integrity or the trust that is placed in them.
And Allah the Almighty knows best.