Admin Fee on Student Let ASTs to pay for bond insurance and chasing documents

I intend to charge a £50 refundable administration fee on new student contracts.

I will refund this IF the tenant completes all the paperwork within 10 days of contract sigining. This includes

• Standing order
• Supplying bonds in cleared funds
• Contract signature including nominating lead tenant
• Signed TDS form
• Signed parental consents for TDS
• Tenant details form

This has several advantages

1. The bonds are all in within the timescale to ensure only 1 bond insurance fee is payable – for late bonds the admin fee will cover the additional insurance fee.
2. Time spent chasing outstanding paperwork is limited or paid for by the fee
3. The costs of chasing up absent tenants e.g. language students, is covered.
4. the costs are related specifically to the tenant who is slow to get their papers together - only those who go past the 10 days are charged.

Q1. Is this legal? And it is legal where parents are involved in paying bonds and rentals?
Q2. Where on the RLA contract is the admin fee shown?!