Their emergence is explained by modern scholars as a result of growth of state machinery, complication of taxation system and the "rapid expansion of land-grant practice that required professional documenting fixation".

[20] According to Romila Thapar, the offices that demanded formal education including that of a kayastha were generally occupied by the "Brahmins, revenue collectors, treasurers and those concerned with legal matters".

[28] Razia Banu has suggested that Brahmin and Kayastha migrants were brought to Bengal during the reign of the Gupta Empire to help manage the state affairs.

[29]: 5–6  According to a legend, a Bengali King named Adisur had invited Brahmins accompanied by Kayasthas from Kannauj who became an elite sub-group described as Kulin.

[33] In early-mediaeval Kashmir too, the term kayastha denoted an occupational class whose principal duty, besides carrying on the general administration of the state, consisted in the collection of revenue and taxes.

Kshemendra’s Narmamālā composed during the reign of Ananta (1028-1063 CE) gives a list of contemporary Kayastha officers that included Gṛhakṛtyadhipati, Paripālaka, Mārgapati, Gañja-divira, Āsthāna-divira, Nagara-divira, Lekhakopādhya and Niyogi.

B. Razia Akter Banu writes that, partly because of Muslim sultans' satisfaction with them as technocrats, many Bengali Kayasthas in the administration became zamindars and jagirdars.

[46] During the British Raj, Kayasthas continued to proliferate in public administration, qualifying for the highest executive and judicial offices open to Indians.

[47][page needed] Bengali Kayasthas took on the role occupied by merchant castes in other parts of India and profited from business contacts with the British.

[51] This classification has increasingly led to feelings of unease and resentment among the Kayasthas, who believe that the communities that benefit from reservation are gaining political power and employment opportunities at their expense.

Thus, particularly since the 1990 report of the Mandal Commission on reservation, Kayastha organisations have been active in areas such as Bihar, Madhya Pradesh, Bengal and Orissa.

[54] Although at that time, prior to the Muslim conquests in the Indian subcontinent, they were generally outnumbered by Brahmins in the Hindu royal courts of northern India, some among these Kayasthas wrote eulogies for the kings.

[55][56] The group of Bhatnagar, Srivastava, Ambashtha and Saxena of Doab were classified by various Indian, British and missionary observers to be the most learned and dominant of the "service castes".

So there is every probability that a number of brahmana families were mixed up with members of other varnas in forming the present Kayastha and Vaidya communities of Bengal.

[74] As the Kayasthas are a non-cohesive group with regional differences rather than a single caste, their position in the Hindu varna system of ritual classification has not been uniform.

The first case began in 1860 in Jaunpur, Uttar Pradesh with a property dispute where the plaintiff was considered an "illegitimate child" by the defendants, a north-Indian Kayastha family.

In the next case in 1875 in the Allahabad High Court, a north Indian Kayastha widow was denied adoption rights as she was an upper-caste i.e. Dwija woman.

[75][76] Hayden Bellenoit concludes from an analysis of those that in the suits originating in the Bihari and Doabi heartlands rulings that Kayasthas were of twice-born status were more likely.

The Hindu texts referenced were Mitākṣarā, the Padmapurāṇa, “original Vyavashta of the Pundits of Kashmir”, Vishvanath Narayan Mandlik's books, (8th to 5th century BC authored) Yājñavalkya Smṛti, Vīramitrodaya (17th century), Bhaviṣyapurāṇa, Skandapurāṇa, Vivādacintāmaṇi of Vāchaspati Misra, Sanskrit Professor Sarvadhikari's literature, Dattakamīmāṃsā, Shyamcharan Sarkar’s Vyavasthādarpaṇa, etc.

[77] Earlier, in Bihar, in 1811–1812, botanist and zoologist Francis Buchanan had recorded the Kayastha of that region as "pure shudra" and accordingly kept them at the par with other producer caste groups like goldsmiths, Ahirs, Kurmis and the Koeris.

William Pinch, in his study of Ramanandi Sampradaya in the north describes the emergence of the concept of "pure Shudra" in growing need of physical contact with some of the low caste groups who were producer and seller of essential commodities or were the provider of services without which the self sufficiency of rural society couldn't persist.

[79] The Raj era rulings were based largely upon the theories of Herbert Hope Risley, who had conducted extensive studies on castes and tribes of the Bengal Presidency.

According to William Rowe, the Kayasthas of Bengal, Bombay and the United Provinces repeatedly challenged this classification by producing a flood of books, pamphlets, family histories and journals to pressurise the government to recognise them as kshatriya and to reform the caste practices in the directions of sanskritisation and westernisation.

[80][clarification needed] Rowe's opinion has been challenged, with arguments that it is based on "factual and interpretative errors", and criticised for making "unquestioned assumptions" about the Kayastha Sanskritisation and westernisation movement.

[83] After the Muslim conquest of India, they absorbed remnants of Bengal's old Hindu ruling dynasties—including the Sena, Pala, Chandra, and Varman—and, in this way, became the region's surrogate kshatriya or "warrior" class.

[92] The Central Bureau of Statistics of Nepal classifies the Kayastha as a subgroup within the broader social group of Madheshi Brahmin/Chhetri (together with Terai Brahmins and Rajputs).