One server was stolen from a branch in Lurgan, County Armagh, in April 2014 and another was lost a month later by a courier firm in Swindon, Wiltshire.
Encryption systems were not good enough to ensure data could not be accessed, the Information Commissioner said.
The company apologised and said it had since reviewed its IT security.
The Information Commissioner's office said the servers, which are still missing, "held large numbers of local and national customer records and employee details".
Under The Money Shop's own rules, servers should have been stored in a separate locked room, but the Lurgan store - and others - did not have rooms available to store them.
It also had a "widespread practice" of moving unencrypted servers between its head office in Nottingham and its branches, the commissioner said. Old customer records were not deleted.
Head of enforcement at the commissioner's office, Steve Eckersley said customers had expected their financial details to be kept safe.
"Our investigations discovered that this wasn't the case and that this information was regularly left exposed when equipment was moved around the country.
"There was potential for fraud and financial loss to customers, which is unacceptable, and in both cases had the data been properly encrypted the damage and distress to customers and the monetary penalty could have been avoided."
Dollar UK, which owns the Money Shop, said: "Since these events took place, Dollar UK has come under new ownership and management, implementing a complete review of IT and systems security, including the replacement of those responsible for managing this essential element of business infrastructure and consumer confidence."

An estimated 40% of cash dispensers are empty, meaning people are unable to withdraw new notes to replace the old ones they have handed in.
There has been widespread disruption since Prime Minister Narendra Modi said in November that 500 and 1,000 rupee notes would no longer be legal.
The move was meant to curb corruption.
It has divided opinion, especially over how the ban was implemented.
Early last month the government scrapped the 500 and 1000 rupee notes to crack down on undeclared money and fake cash.
Deadlines for spending the notes or swapping them for new currency have already passed.
Some people, including those of Indian origin living abroad, will be able to exchange the notes in branches of India's central bank until 31 March 2017 - but the process will be more complicated than going to a regular bank.
Parliament is preparing laws that will make it a criminal offence to hold the old notes from 1 April 2017 onwards.
Together the two notes represented 86% of the currency in circulation and there have been chaotic scenes in India ever since, with people having to spend hours queuing outside banks and cash machines which have been running out of money.
ATM queues and cash withdrawal limits mean getting currency can still be tricky, and there have been several changes of the rules around how much money people can access or deposit.
The government hopes the measures will encourage more people to have bank accounts and move towards a society less reliant on cash.
But there are concerns that many poorer people and those in rural areas have yet to get bank accounts.
Local firms which allow people to make digital payments both online and in shops have reported a surge in transactions as people look for cashless alternatives.
The government says the move has been a success with the banks flush with cash and significant increases in tax collection.
But critics argue the move has failed to root out corruption and unearth illegal cash, since most of the money in circulation has been put back into the financial system. Instead, they say, the economy which was growing at a rapid pace, has slowed down significantly.
Payday lender The Money Shop has been fined £180,000 after losing computer servers with thousands of customers' financial details.
[NEXT_CONCEPT]
There have been long queues outside many banks in India as people tried to deposit discontinued banknotes ahead of a deadline that has now passed.