No, it won't. You do not need to maintain a minimum balance in your cash account for it to remain open. We also do not charge any inactivity fees.
Please note, from time to time the company may do an audit and if you do not have any holdings or cash or traded in your trading account after 12 months from opening the account (or portfolio), we may contact you via email to confirm that you still wish to have it open, and to deposit funds or transfer stocks to keep it open within a certain time period. If we do not hear back from you, then your trading account may be closed.
If you find that you can't login due to inactivity and for more information please visit Why has my account or portfolio been automatically/closed?