The precise information requested is not available.
The cost of making payments to pensioners depends on the payment method they choose. The average costs of each payment method are:
Cost (£) Payment into a bank account 0.01 Payment into a Post Office card account 0.80 Payment by cheque 1.79 Source: Corporate Banking and Methods of Payment.
Making payments less frequently (four weekly, rather than weekly) would appear, on the face of it, to reduce the Department's payment costs as fewer payments would be made each year. It is not possible to say exactly what impact on costs this would have as it would depend on a variety of factors—including customer behaviour and third party charges.