IMS spends an estimated $300,000 annually on sponsorships, especially for the Hawke's Bay Rescue Helicopter Trust, rugby and basketball.
MYOB general manager James Scollay said sponsorships would be considered as they came due for renewal, but ASX-listed MYOB had many shareholders to answer to, unlike IMS.
"That kind of commitment from that size business is more about his (Mr Atkinson's) personal contribution," he said.
The IMS brand would continue "in the foreseeable future" and it would be "business as usual".
Mr Atkinson collects 75 per cent of the purchase price, with fellow shareholder and IMS chief executive Doug Jopling collecting the balance. Mr Jopling will remain in his role and join Mr Atkinson on an advisory panel to ensure a smooth transition.
After 13 years in the meat industry at Whakatu, Mr Atkinson founded IMS in 1983.
Profit magazine, in 2013, voted Atkinson the most influential man in Hawke's Bay and he has now reached a crossroads.
Had council amalgamation happened, he said he was "prepared to consider standing" for Hawke's Bay mayor when asked by Hawkes Bay Today.
"I'm 65 now, so it's time to start thinking about the future - you don't know where your health is going to take you," he said.
"I need the rest of the year to think about things. I have to think if I want to stand for the DHB again and I have to negotiate with the Hawke's Bay Power Consumer's Trust to see if they will appoint me to Unison again for another term."
He is looking for a new office to operate his non-business interests.
"I have had very good staff working for me at IMS that have supported me in my DHB and other work. The first thing I have to do is find some way I can operate those rolls outside IMS."
The 21 staff "are like a family", with half working at IMS for more than a decade. It is the third New Zealand payroll company purchased by MYOB. Last year it bought PayGlobal and in May it bought Ace Payroll.
"We estimate over 30 per cent of the New Zealand workforce is paid using MYOB software and we're committed to providing easy online payroll solutions for all employers - whether they have just one employee or employ over 500 staff," MYOB general manager James Scollay said.
MYOB has operated in New Zealand for more than 20 years and has 1.2 million businesses across Australia and New Zealand.