Is it permissible to open a bank account with a minimum deposit (such as one thousand pounds) and obtain a checkbook to ensure dealings with companies, knowing that the value of purchases far exceeds this amount (such as ten thousand pounds)?

Opening a deposit account in an Islamic bank and obtaining a checkbook is permissible. However, with a usurious bank, it is not permissible except out of necessity or pressing need, because placing money in it assists the bank in its prohibited usurious dealings, as Allah Almighty says: [And do not cooperate in sin and aggression]. As for issuing checks as a guarantee for companies, there is no objection to it, and it is in accordance with the rulings of Islamic law that call for the preservation of people's rights. You should either have a balance covering the value of the check or be able to pay it upon request.