Unpaid director remuneration

Ltd Co client,...

... one of the directors has been underpaid in the last two years versus their contract, i.e. paid £1200 gross per month instead of £1300 gross per month (payroll processed at £1,200 pm therefore, no PAYE issues).  How should this debt to the director be acknowledged in the accounts ended 31.12.11?  It is not certain if this underpayment will be corrected in the next 9 months, just when the cashflow is robust.