Revenue collection refers to the process of collecting income or funds for the government from various sources. It is an essential aspect of administration and consolidation under the Khaljis and Tughlaqs, who were rulers of the Delhi Sultanate in medieval India. The revenue collection system during this period played a crucial role in the functioning and stability of the state.

Administration under the Khaljis:
1. Centralization of Power: The Khaljis aimed to centralize power and establish a strong administration. They abolished the office of Naib-i-Mulk and introduced the office of Wazir, who had extensive powers.

2. Revenue Reforms: Alauddin Khalji, the most famous Khalji ruler, implemented several revenue reforms to increase the state's income.
- Market Control: Alauddin introduced the system of the Diwan-i-Riyasat, which regulated prices and ensured that essential commodities were available at fair rates. This control helped increase revenue as the state could levy taxes on these goods.
- Taxation: Alauddin imposed heavy taxes on various sectors of society, including the agricultural sector.
- Land Revenue System: The Khaljis introduced the Dahsala system, where one-tenth of the produce was collected as tax. This system was efficient and helped increase revenue.

Administration under the Tughlaqs:
1. Centralization of Power: The Tughlaqs also aimed to centralize power and establish a strong administration. They introduced the office of the Amir-i-Shikar, responsible for hunting and maintaining order.

2. Revenue Reforms: Muhammad bin Tughlaq, one of the prominent Tughlaq rulers, implemented several revenue reforms.
- Token Currency: Muhammad bin Tughlaq introduced token currency, known as the "silver tanka." However, this experiment failed, leading to economic instability.
- Irrigation Reforms: The Tughlaqs focused on improving irrigation systems, as agriculture was a major source of revenue. They built canals and reservoirs to enhance agricultural productivity.
- Taxation: The Tughlaqs imposed heavy taxes on various sectors, including agriculture, trade, and professions.

Importance of Revenue Collection:
1. Financial Stability: Revenue collection was crucial for the financial stability of the state. It provided funds for administration, defense, infrastructure development, and welfare activities.

2. Governance and Administration: The revenue collection system helped in maintaining law and order, providing justice, and ensuring the smooth functioning of the administration.

3. Economic Development: The revenue collected was invested in various sectors, such as agriculture, trade, and infrastructure, promoting economic development.

4. Military Strength: A strong revenue collection system enabled the rulers to maintain a powerful military, which was essential for defense against external threats and expansion.

In conclusion, revenue collection played a vital role in the administration and consolidation under the Khaljis and Tughlaqs. Through various reforms and taxation measures, these rulers aimed to increase the state's income, ensure financial stability, and promote overall development.