Why don't cheques clear instantly?
Cheques are paper items, which are physically transferred between banks. Although the paying bank receives some of the data electronically, the cheques themselves must also be transferred. This is so that they can be examined by the paying bank for security and fraud prevention purposes, to ensure that the cheque has been made out correctly and to make the decision whether to return a cheque unpaid.
Despite the central clearing timescales individual banks may decide to allow customers to withdraw cheque funds more quickly. However, if a cheque bounces before the end of the 6th working day after paying in, then the bank may seek to reclaim the cheque funds.