Even if you don't issue a written contract, you are under a legal duty to provide most employees with a written statement of main employment particulars within two months of the start of their employment with you.
The written statement is not itself the contract but it can provide evidence of the terms and conditions of employment between you and the employee if there is a dispute later on. bla bla bla
Some people get confused between the terms 'contract' & 'written Statement' bless...