The margin requirements for a covered put (short stock, short put) are as follows:  

Initial $5.00/share and below: greater of $2.50/share or 100% and no requirement on the short put  

Initial above $5.00/share: greater of $5.00/share or 50% and no requirement on the short put  

Maintenance below $2.50/share and the put option is out of the money: $2.50/share  

Maintenance below $2.50/share and the put option is in the money: $2.50/share + 100% of the in the money amount  

Maintenance $2.50/share to $5.00/share and the put option is out of the money: 100% of the stock  

Maintenance $2.50/share to $5.00/share and the put option is in of the money: 100% of the stock + 100% of the in the money amount of the put  

Maintenance above $5.00/share to $16.67/share and the put option is out of the money: $5.00/share  

Maintenance above $5.00/share to $16.67/share and the put option is in of the money: $5.00/share + 100% of the in the money amount of the put option  

Maintenance above $16.67/share and put is in or out of the money: The maintenance margin requirement is based on a comparison of the stock position's value to the absolute value of all marginable stocks in the account (long and short).