Jenison (Jenyson, Genyson), Thomas (d. 1587), auditor general of Ireland, was the eldest son of Robert Jenison of Yokeflete, Yorkshire, England, and his wife Agnes, daughter of William Wren of the Isle of Ely. In early 1550 he entered the royal service and was dispatched to the north of England to inspect the royal financial accounts there, after which he became auditor of the court of admiralty. He lived in London, where he leased a property in the parish of St Giles Cripplegate. About this time, he married Elizabeth, daughter of Edward Birch of Sandon, Bedfordshire, groom-porter to King Henry VIII. They had five sons and a daughter.
He was appointed auditor general and auditor of the treasurer at war's accounts on 10 February 1551, in which capacity he verified the accounts of the Dublin administration. His tenure was abruptly terminated, however, in 1553 when he was implicated in the corruption and mismanagement of the vice-treasurer of Ireland, Andrew Wise (qv), and was replaced by Valentine Browne (qv) (d. 1589) on 12 December of that year. Wise was imprisoned, but Jenison was more fortunate, receiving a pardon (c.1553). However, he was alarmed by further investigations into financial malpractice within the Dublin administration that continued throughout the mid 1550s. Probably fearing that he might yet suffer a heavy fine or imprisonment, he threatened his successor as Irish auditor, for which he was censured by the royal authorities in April 1556 and compelled to enter a recognisance of £100,000 for his future good behaviour.
On 25 November 1560 Jenison was appointed controller of the works and keeper of the store at the castle at Berwick, a post he continued to hold until at least 1577. For most of that period, however, he administered that post through a deputy, for by 24 May 1566 he had been reappointed auditor general of Ireland. Thereafter he served on a number of important commissions connected with financial affairs, including commissions (1576, 1578) to discover concealed lands of dissolved monasteries and attainted landowners, and a commission in 1576 to recover the debts owed to the queen. However, he continued to attract controversy and was repeatedly criticised by the English privy council for failing to produce regular audits of the queen's Irish accounts. In 1574 the English council reproached him for failing to complete his audit of the accounts from three years beforehand, and did so again in 1578 for his failure to complete the 1574 audit. He justified his tardiness, not unreasonably, by pointing to the generally chaotic state of the Irish exchequer accounts. Moreover, it is clear that political pressure was brought to bear on him by leading actors in the royal administration in Dublin who were desperate to disguise the scale of the queen's spiralling military expenses in Ireland. Two lord deputies, Sir Henry Sidney (qv) (1565–71, 1575–8) and Sir William Fitzwilliam (qv) (1571–5), both shielded him from London's censures, particularly Sidney, who granted him three general pardons between 1575 and 1578.
Significantly, Jenison accompanied Sidney back to England on the lord deputy's ignominious recall in 1578, and in his absence his government colleagues in Dublin were highly critical of both him and Sidney for their stewardship of the queen's Irish finances, suggesting none too subtly that they had embezzled crown revenues for their own private benefit. He returned to his duties in Dublin in August 1580 following the appointment as lord deputy of Arthur Grey (qv), who was on friendly terms with Sidney and who proved to be notoriously lax in his management of Irish finances. However, Jenison's effectiveness in office during the 1580s was limited by repeated attacks of gout, from which he received only a brief respite in 1583–4. As well as warding off suspicions of corruption, he was also embarrassed by the decision of his eldest son William to convert to catholicism. In June 1584 he was appointed to the commission to survey the lands of the rebels who had been attainted following the Desmond rebellion of 1579–83, but he was replaced due to illness before it began its work and took no part in the subsequent survey. Late in his career, he left proposals for reform of the revenue-gathering apparatus in Ireland, calling for greater exchequer involvement in, and supervision of, the collection of various types of revenue accruing to the Dublin administration.
As early as 1581 he sought to surrender his office to Christopher Peyton, and on 7 June 1587 the two men signed an agreement to that end, Jenison finally leaving his office on 20 October of that year. On his death, shortly after 17 November, a number of chests containing accounts relating to the payment of army captains were removed from his residence and thereby prevented from being viewed by his successor as auditor general. The lord deputy, John Perrot (qv), on noting his death, stated pointedly that Jenison had ‘lived like a hog and died like a dog’ (CSPI 1586–8, 475). Certainly, and despite his claims to have suffered financially from his service in Ireland, he died a much wealthier man than his father, who had been a relatively minor landowner. He had purchased an estate at Walworth in Durham and refurbished the castle there, which became his main English residence; he had other houses in Dublin, Berwick, and London. In his will he also disposed of property in Yorkshire, Gloucestershire, Northamptonshire, Somerset, and Caernarvonshire. Most of this property was bequeathed to his second son John after he disinherited his eldest son William for his continued adherence to catholicism. William settled in Kildare and his son Robert became a Jesuit.