Add a number of months to a date

5

Something like this should work

Date(
  Year(CurrentDate) +
    RoundDown((Month(CurrentDate) + IntervalPeriod - 1) / 12, 0),
  Month(CurrentDate) +
    IntervalPeriod -
    12 * RoundDown((Month(CurrentDate) + IntervalPeriod - 1) / 12, 0),
  Least(
    Day(
      Date(
        Year(CurrentDate) +
          RoundDown((Month(CurrentDate) + IntervalPeriod - 1) / 12, 0),
        Month(CurrentDate) +
          IntervalPeriod +
          1 -
          12 * RoundDown((Month(CurrentDate) + IntervalPeriod) / 12, 0),
        1
      ) - Days(1)
    ),
    Day(CurrentDate)
  )
)

You’d use Paid Terms instead of IntervalPeriod