arrear

n. That which is behind in payment, or which remains unpaid, though due; esp. a remainder, or balance which remains due when some part has been paid; arrearage; -- commonly used in the plural, as, arrears of rent, wages, or taxes. Locke. [ 1913 Webster ]

For much I dread due payment by the Greeks
Of yesterday's arrear. Cowper. [ 1913 Webster ]

I have a large arrear of letters to write. J. D. Forbes. [ 1913 Webster ]

In arrear or
In arrears, behind; backward; behindhand; in debt. [ 1913 Webster ]