TLDR - Admin charge and if it's happened three times, he won't be able to renew next season.
Missed instalments are subject to a £15 default administration charge per missed instalment. The Club will notify the Season Ticket Holder when a payment has been missed and when the administration charge has been triggered. The default administration charge and the missed instalments will then both be payable by the Season Ticket Holder by calling the City Sales Centre on 0344 815 5000 (Option 1) immediately. 8. Missed instalments and/or a failure to pay the administration charge which has been triggered under Condition 7 above will result in the Season Ticket and Supporter Number(s) linked to the missed instalment account being frozen. The Season Ticket will be deactivated and will not permit entrance to the Stadium until payment is made. No additional tickets for any match in which the Club is involved can be purchased under the Supporter’s account while it is frozen – this applies to all Season Tickets paid for by the same Direct Debit. Once the appropriate instalment and administration charge has been paid and received by the Club, the account will be unfrozen and all applicable Season Tickets reactivated. The Club reserves the right to take whatever action is required (including the appointment of a third party) to recover any sums due and payable. 9. Any supporter who has missed Direct Debit instalments three (3) times or more during a Season will not be eligible to renew their Direct Debit the following season. 10. If any supporter has two (2) or more outstanding instalments on their account at any time, the lead purchaser and affected Season Ticket Holder (if different) will be contacted and given ten (10) days’ notice to make the relevant payment to update their account. Failure to make the relevant payment within the required ten (10) days will result in the affected Season Ticket(s) being cancelled without reimbursement or future correspondence from the Club. 11. Any supporter who wishes to change their bank details must notify the Club before the 15th of the month in which the payment is due to be taken. 12. If during the Direct Debit Scheme, the supporter wishes to cancel their Direct Debit Scheme and change the method of payment, they must contact the Club no later than 15 days in advance of the next due instalment. The supporter must pay any outstanding balance against the Season Ticket when informing the Club of their intent to cancel the Direct Debit Scheme. For the avoidance of doubt, if any outstanding balance against the Season Ticket is not paid at this time, the Club reserves the right to exercise any of 19 its rights set out in Conditions 8, 9 and 10 above. This is merely a right to amend the method of payment and not a right to cancel the Season Ticket. - From the Ts and Cs