How to Place a Bull Put Spread on Interactive Brokers TWS

You've read about the bull put spread and you know the shape of the trade: sell a put, buy a lower put, collect a credit. Knowing the strategy and knowing where to click in Trader Workstation are two different skills. This post is the second one, specific to TWS.

Start from OptionTrader, not a plain order ticket

In TWS, don't build a spread by placing two separate option orders. Right-click the underlying in your watchlist and choose Trading Tools › OptionTrader (or open it from the New Window menu). OptionTrader lays out the full chain, calls on one side, puts on the other, with strikes down the middle, and lets you select multiple legs directly off the chain instead of typing them into a ticket by hand.

This matters because TWS needs to recognize your two legs as one combo, not two unrelated trades. Building it off the chain is what makes that happen automatically.

Selecting the legs

Say ABC is trading at $200 a share and you're bullish. On the put side of the OptionTrader chain, for the expiration you want:

Left-click the bid on the $190 strike to stage a sell
Left-click the ask on the $180 strike to stage a buy

Each click adds that leg to the order line building at the bottom of the window. TWS will show both legs stacked with their strikes, and once it recognizes they share the same underlying and expiration, it groups them into a single combo automatically. If you only see two separate single-leg tickets instead of one combo line, you clicked into the wrong panel, back out and reselect from the chain.

Reading the combo price

Once both legs are staged, TWS shows you a combined bid/ask for the spread as one number, not two. For this example: selling the $190 put and buying the $180 put nets a credit, and TWS will display that combo price with a plus sign or clearly marked "CR" for credit.

This combo price is what you're trading, not the individual leg prices. If you added it up by hand ($3.00 collected minus $1.00 paid, so a $2.00 credit) and the ticket shows something different, stop and check that you sold the higher strike and bought the lower one. A reversed order flips this into a debit spread with completely different risk.

Setting the order type and limit price

In the order line, set:

Order type: LMT (limit), not MKT. A market order on a combo exposes you to the spread on both legs at once, worse than a market order on a single option.
Limit price: your net credit, $2.00 in this example, entered as the combo price, not split across the two legs.
Time in Force: DAY if you only want today's price, or GTC if you're willing to leave the order working across multiple sessions until it fills or you cancel it.

TWS will also show you the current combo mid-price (halfway between the combo's bid and ask) as a reference. That's usually a reasonable starting limit if you want a realistic shot at a fill without giving away edge.

Check the margin impact before you transmit

Before hitting Transmit, look at the Order Preview panel. TWS shows you the change to your buying power and margin requirement from this specific order, not just your account totals. For a defined-risk spread like this one, it should reflect roughly the max loss, the $10 gap between strikes minus your $2.00 credit, times 100 shares, so around $800 for one contract, not the much larger amount a naked short put would require.

If the number in Order Preview looks closer to what a naked put would cost, the legs likely aren't combo-linked the way you intended. Cancel, rebuild from the chain, and check again before transmitting.

Before you click Transmit

Order line shows one combo, not two separate single-leg tickets
Sold the higher strike, bought the lower strike
Combo price shown as a credit (CR), matching your own math
Order type is LMT, not MKT
Time in Force set on purpose
Order Preview margin impact matches a defined-risk spread, not a naked put

That last check catches more mistakes than any other step here. TWS will tell you the real number before you commit capital to it, so read it.

Past the basics

The screens and shortcuts above cover the mechanics of this one trade. If you're on Interactive Brokers day to day, Impara la TWS goes a lot deeper into TWS itself, order types, hotkeys, the full OptionTrader workflow, screen by screen. Worth a look once you're comfortable with the concepts and want to get faster at the platform.