A previous ruling set a precedent for how the IRS treats pension distributions that are paid in installments. 

Letter Ruling 7802035  states that where a distribution from an employer’s qualified pension plan is received in more than one installment, each installment may be rolled over within 60 days after receipt, as long as the total distribution is received within the same taxable year, and as long as the final installment is rolled over on or before the sixtieth day after the day on which it is received.