Use TWS Preview to inspect an order’s margin impact

Quick answer

Use Preview on a proposed TWS order to check estimated margin impact before sending. Confirm the contract and size first. An estimate is not a guarantee that the eventual order will be accepted or filled.

Educational software guidance. Trading involves risk. Read the financial and information disclaimers.

Step by step

1 Create the intended order ticket in the correct account without sending it.
2 Check symbol, expiry, side, size, and order type.
3 In Mosaic, open the small arrow beside Buy or Sell and choose Check Margin Impact. Read the Order Preview and its Current, Change and Post-trade margin columns. Do not click Transmit to check the estimate.
4 Compare the estimate with the account’s available resources and any broker warning.
5 Close or revise the ticket if it does not match your intent; submit only as a separate planned trading decision.

A practical example

You plan a trade but first want to see its estimated effect on funds. Open Preview for the exact contract and size. Read the estimate, then close the ticket if you are only checking. A preview of one contract does not tell you the cost of a different month or size. It also does not promise that the estimate will stay the same as prices and the account change.

Illustrative scenario, not a record of a trade placed during this review.

Screen reference

Paper Order Preview with quantity, limit price, route, time in force and a price warning — An illustrative one-share draft was opened through Check Margin Impact, then closed without transmitting. The symbol and price are examples, not recommendations. The account-total section is excluded. Captured in TWS paper mode on 3 October 2026. Open the image for full size.

Initial Margin, Maintenance Margin and Position rows from a paper order preview — The numeric columns are Current, Change and Post-trade, from left to right. This excerpt excludes account totals. These are simulated estimates for the example draft, not a live requirement or a fee quote. Captured in TWS paper mode on 3 October 2026. Open the image for full size.

How to confirm the result The preview should describe the exact proposed order rather than a different contract or size.

Mistake to avoid

Do not run repeated automated previews in a tight loop; IBKR warns against overusing WhatIf requests.

Common questions

Does Preview place the trade?

Use the preview function, then treat sending as a separate action.

Is the estimate fixed until I submit?

No. Account and market conditions can change.

TWS says Submitted but the order has not filled TWS order stuck on PendingSubmit TWS order is Inactive: find the actual reason TWS error 201: read the order rejection reason

Financial and information disclaimers

Financial disclaimer

These guides explain software. They are for education, not financial, investment, tax, or legal advice. No example is a suggestion to buy or sell a product or use a trading strategy. Trading can lose money, including all funds you put at risk. With margin, futures, short sales, or some options, losses can exceed your starting funds. Automation can fail, send duplicate orders, or act late. Stops do not guarantee a fill or a price. Review your orders and positions, and seek advice from a qualified professional for your own needs. Paper trades, examples, and past results do not predict live results or promise a profit.

Information disclaimer

This is general help based on the sources and check date shown on the page. Screens, settings, fees, data access, and product support can change or differ by app version, account, country, and broker. The content may contain errors or become out of date; accuracy, completeness, and continuous service are not guaranteed. Check current broker and app instructions before acting. Screenshots show where controls are; they do not prove that an order test passed. This guide does not replace broker terms or risk notices. References to IBKR and TradingView identify their products and do not imply their endorsement of this guide.