Garuda Purana deals with the journeys of a soul after it discards the body. This is a dialogue between Lord Mahavishnu and His mount Garuda. Chapter 3 deals with the torments of Yama. Here Chitragupta, his role, his helpers and aides are described. Without quoting the Sanskrit text, I reproduce below the English translation by Ernest Young and S.V.Subrahmanyam from their book 'The Garuda Purana.
An Account of the Torments of Yama.
1. Garuḍa said: What are the torments like that the sinful suffers, having passed along the way of Yama into the abode of Yama? Tell me this, O Keśava.
2. The Blessed Lord said: Listen, O Descendant of Vinatā. I will tell it to you from the beginning to the end. Even at the description of hell you will tremble.
- Four and forty yojanas, O Kāśyapa, beyond the city of Bahubhīti, lies the great city of the King of Justice.
4-5. The sinful man cries when he hears the mingled wails of 'Oh, Oh,' and having heard his cry, those who walk about in the city of Yama.
All go to the door-keeper and report it to him. The doorkeeper Dharmadhwaja, always stands there.
6. He, having gone to Chitragupta, 1 reports the good and evil deeds. Then Chitragupta tells it to the King of Justice.
7. The men who are Deniers, O Tārkshya, and always delight in great sin; these are all, as is proper, well-known to the King of Justice.
8. Nevertheless, he asks Chitragupta about their sins. Chitragupta, although he is all-knowing, enquires of the Śravaṇas 1.
9. The Śravaṇas are the sons of Brāhmaṇ who wander in heaven, on earth, and in the nether regions, hear and understand at a distance, and see a long way off.
10. Their wives have a similar nature, and are called, distinctively, Sravanīs. They know accurately all that is done by women.
11. These report to Chitragupta everything that is said and done, openly and secretly, by men.
12. These followers of the King of Justice know accurately all the virtues and vices of mankind, and the karma born of mind, speech and body.
13. Such is the power of these, who have authority over mortals and immortals. Thus do these truth-speaking Śravaṇas relate the actions of man.
14. To the man who pleases them by austerity, charity and truthful speech, they become benevolent, granting heaven and liberation.
15. Knowing the wicked actions of the sinful, those truth-speakers, relating them before the King of Justice, become dispensers of misery.
16. The sun and moon, fire, wind, sky, earth and water, the heart. Yama, day and night, the two twilights, and Justice--know the actions of man.
17 The King of Justice, Chitragupta, Śravaṇas, the sun and others see fully the sins and merits of the embodied being.
18. Then Yama, having assured himself concerning the sins of the sinful, summons them and shows them his own very terrible form.
Hence Chitragupta is just not the record keeper of Yama, but an able lieutnant in discharging Yama's role as the upholder of Dharma.