History - Ancient India
Kayastha ministers find mention in Hindu mythology. Prior to the Raghuvanshis, Ayodhya was ruled by Mathur Rulers, progeny of Chitragupta.
by Chitragupt Pariwar (Hum Kayasth) on Tuesday, August 10, 2010 at 3:01pm
The Kayastha who are represented by the "Kayath" or the hereditary caste of the scribes of the present day, formed originally a sub-military class. The Anthropological Survey of India conducted a survey during the British Raj which concluded that the Kayastha community were also influential during the Mauryan period as administrators. Also, many proof have been found that the Hindu Kings used to grant lands to the Kayasthas, a practise enjoyed only by a particular caste. Also, it is but logical to consider the status of the Kayasthas when Sanskrit was the state language under the Hindu Kings.
The Kayastha were one of the most influential Caste in Kashmiri politics around 7th century  (ref. Rajatarangini).In these and contemporary Sanskrit literature we come across the Kayasthas being described as kings, financiers and advisers. King Lalitaditya Muktpida was one glorious King of a Kayastha dynasty of Kashmir.
The various scripts used by the Kayastha during most of the Ancient period can only be conjectured, but Brahmi certainly was extensively used and often praised as the scrit of the Vedas given by Bhagvaan Chitragupt himself.
Islamic and Pre-independence India
The Kayastha caste's affinity for learning and socio-economic status, both enabled and dictated that the community develop expertise in the changing administrative policies and official languages, as different empires were established in India. The community learned and adapted terminology to Persian, Turkish, Arabic and later Urdu in Islamic India. Importantly, the community created, maintained and developed empire-wide administrative practices in monetary policy, jurisprudence and taxation.
The script used during this period was majorly Perso-Arabic script.
Notable example include Raja Todar Mal who translated the ‘Bhagwat Purana’ into Persian . Raja Todarmal was one of the `Nav Ratans' of Emperor Akbar who founded and gave proper shape to `Revenue System' during Mughal Empire.
These roles continued into the colonial era, where many Kayasthas were the first to learn English and become civil servants, tax officers, junior administrators, teachers, legal helpers and barristers. During this period, Kayastha community members were more likely (than other communities) to undertake academic training in England and often rose to the highest positions accessible to natives in British India. As a consequence of their relatively large proportion amongst Indian students abroad, and because many hit ceilings of progression because of racial status, community members played pivotal roles in the early political groups that questioned British rule in India.
The script used during this period was Kaithi. The name makes a very clear reference to the creators, the Kaystha are often referred as "Kayath" in middle ages. Kayasthas have a unique distinction of having a script - Kaithi - associated with their name. Kaithi (also known earlier as Kayati, Kayathi or Kayasthi), similar to Dev Nagri, was used mainly by Kayasthas in northern India. It has its own Unicode now and was the major contender in the race to become national script but was left behind due to being not known to masses.
Many Kayasthas were successful in adapting to post-independence India, becoming civil servants, bureaucrats and lawyers. The community's traditional association with higher education also led to heavy immigration to the west in the 1970s and 1980s as community members sought increased educational and research opportunities. Notable examples include the first President of India, Dr. Rajendra Prasad, the third Prime Minister, Lal Bahadur Shastri, social and religious reformer Swami Vivekananda, freedom fighter Subhash Chandra Bose and film-star Amitabh Bachchan.