Rochester will be getting a $104,536 refund from the Plymouth County Retirement system. Marion will get a bill for $110,000. And Mattapoisett will be told to ante up $9,565.

The up and down adjustments come after the realization that Old Rochester Regional School District pension system costs had been wrongly divided among the three towns for years.

The error occurred with the distribution of Plymouth County Assessments for retired school staff among the three towns – Marion, Mattapoisett, and Rochester.

The Old Rochester Regional budget is divided among the towns. Rochester pays 36 percent of the overall budget.

During the Old Rochester Regional School Committee meeting on March 14, Rochester Town Administrator Richard LaCamera said that since 1984, Rochester has been charged much more than its share.

Katie Isernio, business administrator for the district, said that Rochester has been overcharged $104,536, while Mattapoisett and Marion owe money to the district. Mattapoisett owes the district $9,565 and Marion owes $110,000.

“I’m not sure anybody realized the magnitude of the problem,” LaCamera said. “We feel the issue ought to be resolved now. Let’s get it over with so we can move on.”

The School Committee voted to pay back Rochester in full, effective in 2013.

Though this will have no impact on Old Rochester Regional’s 2013 budget, it raised the question: should Marion and Mattapoisett also have to pay the district back in full in a one-year period?

Old Rochester Regional’s budget remains unaffected because their budget would still receive the same amount of money in 2013, only the funds between the three towns would be shifted so that Rochester would not be bear the largest burden.

Because both Marion and Mattapoisett owe money to the district, the School Committee was considering what would have the least impact on the towns.

The towns would have to make adjustments to their individual budgets to account for the amount they owe to Old Rochester Regional.

To offset the increased costs to the Marion and Mattapoisett, Isernio and Superintendent Doug White suggested that the School Committee consider allowing the two towns a two-year option to pay back the amount owed.

Since the March 14 meeting both towns have agreed to the one-year payback term Isernio said.

Previously, Marion town officials have asked that they be allowed two years to pay back the district, while Mattapoisett officials did not make a preference due to their having the lower amount of money owed, she said.

Mattapoisett Town Administrator Michael Gagne said that another error was discovered in which Mattapoisett was overcharged.

Gagne said that the town was billed for the pension and health insurance of a retired employee at Old Rochester Regional who was not a Mattapoisett resident.

This, he said, was discovered shortly after Rochester officials discovered the error with the pension assessments.

Gagne said the one-year payment plan for the $9,565 the town owes to the district, would not affect the town’s budget in “a tremendous way.”

The district will reimburse Mattapoisett for the error with the one retired employee. This amount will be deducted from the town’s 2013 assessment to the district, leaving the town with $9,565 to pay.

“There’s a plethora of problems there, but for us, this is not an awful lot of money,” Gagne said. “It’s going to end up washing out even for us.”

Gagne said that because the problem with the pension assessments occurred as far back as 1984, there is no way to pinpoint the cause of the problem.

“I think the situation with the errors was made long before any of us were in our positions with the district,” he said. “We can’t really ask the question because no one really knows. I think it’s good that Richard LaCamera caught the error. Let’s get it straight.”

The School Committee members agreed to further discuss the issue with Marion and Mattapoisett town officials before the 2013 assessments are distributed.