This is not a ShortNakedPut, but a CashSecuredPut.
We agree.We are talking about the put seller and their requirementsin a cash account. Bringing in the put buyer is extraneous to the question of the Original Poster.The notion that you can never lose more than the strike price - premium is only true from the put seller's point of view.
We agree.We are talking about the put seller and their requirements. Bringing in the put buyer is extraneous to the thread of the Original Poster.
Of course that is correct. You are misinterpreting my post. The requirement in a cash account is met through cash in the account +the premium received. the Put seller can than use that cash to meet his obligations to the seller. The premium received is his property which he can use to meet his obligation to the seller.. For a cash account, the requirement is ALWAYS the ENTIRE strike price and NOT strike price - premium.
That is not correct in a cash account. There cannot be any additional required even if the stock goes to zero There is a different issue regarding the possibility of early assignment and the customer ends up with a loss. That is a discussion for another day.
So, can one say that it's just temporary? Ie. with a lag of 1 day (settlement time) the net cash requirement reduces?The next day the OP is implying that the premium received is not really his till the next day. Therefore on the trade date T DA is requiring more cash day one in the account than other brokers.

I don't care what he is implying.The next day the OP is implying that the premium received is not really his till the next day. Therefore on the trade date T DA is requiring more cash day one in the account than other brokers.
No disagreement.Everything else is a discussion of semantics.
$400 is locked up.
$100 is what their credit was, and $300 comes out of their settled cash.
Again no disagreement. the OP is saying that he needs $400 already in his account to meet the requirements. Other brokers say that he only needs the $300 in the account+the $100 premium from the sale of the option.I don't care what he is implying.
From TD's own website:
In a cash account, you will be required to hold enough cash to buy the underlying security if assigned. The typical option contract represents 100 shares of stock, so in the example above, you have been required to hold $9,700 ($97 x 100). This cash cannot be used for other account activities until the short put position is closed