Just to make sure it is clear: You do not have any legal grounds to refuse to return them, regardless of whether they do or do not agree in advance to give you a receipt. I hear you saying it is your intent to to return them - I'm not saying you're not. But your initial question was, does their refusal to agree to give you a signed receipt give you justification to refuse to return them, and the answer to that is, No. They will have no reason to deduct anything from your check if you return the property.

If they do make any illegal deductions, you can file a claim for unpaid wages.