In arrear means some of the debts already due but not yet received by the company and recorded as an income e.g the company is usually bill a customer for a regular monthly commission $3000 in the 10th day of the following month. So, at the end of accounting period at 31 December, 2007, the company should has an income of $2000 but only has the right to bill this customer in 10 January, 2008. An arrear of $2000 has then to be recorded in the accounts as commission in arrear and in the current assets of the balance sheet of the company as at 31 December, 2007.
Trade deposit, payment received in advance means these items are to be reflected in next year's account e.g. rent $2700 received for the month from 21 December, 2007 to 20 January, 2008 with the accounts closing date at 31 December, 2007. $900 will be recorded as rental income in that period while the remaining $2700 will be put as a current liability as Rent received in advance.