If you enter a limit order to sell the broker knows with 100%certainty whether you have enough cash in the account. Premium received is cash like any other cash in your account. +It has been correctly pointed out by Van.. that the cash must be equal to the strike price in a cash account.
Can you show where does TastyTrade show that it only requires strike - premium for cash-secured puts?
https://support.tastyworks.com/support/solutions/articles/43000435285-cash-secured-put#:~:text=The buying power requirement for,buying power requirement is different. I never criticize people. I let people reveal themselves. Your post below is a prima facie example,
SELLING AN OUTRIGHT PUT REQUIRES THE TOTAL CASH-SECURED AMOUNT The buying power requirement for a cash-secured put is the (strike price) × (number of contracts) × (option multiplier). The premium received from the sale of the put can be applied to the initial requirement. EXAMPLE OF SELLING A CASH-SECURED PUT Sell to open 6 Mar 11 puts at $0.75 = $0.75 x 6 qty x 100 = $450 credit received 6 x 11 x 100 = $6,600 cash-secured amount When you are entering a trade, has the premium been received?? No. It states very clearly in the very first sentence: To sell the put it requires TOTAL CASH-SECURED AMOUNT which is NOT offset by any premiums. It's not our problem that OP can't read. If English is his second language, then he should take more ESL courses. You need to learn to read as well to troll better.
That's the question. Normally it should be the same with all brokers b/c the risk is clearly defined; there is not any risk for the brokers b/c of the cash collateral in full (creditrcvd + cash = strike, and with such a CashSecuredPut there is not any risk that is > strike). Yes, also at TradeStation. Something suddenly changed on Thursday b/c it did not let me open another such CashSecuredPut position, but which it did all the time in the past even up to some minutes ago in a previous trade. There was enough settled cash available which combined with the credit gives a value that is more than the strike.
TD making a change would end up with more people griping. Possibility the OP is living under a release restriction which would have affected the account(s) and not applied firm-wide.