I was hoping that someone here on ET has used TWS Scale Orders through the API. Here is what I see. I submit orders as follows (e.g.): order.m_totalQuantity = 500 order.m_orderType = "SCALE"; order.m_scaleComponentSize = 100; order.m_scalePriceIncrement= 0.01; In return I get the following error message: Error validating request:-'ob' : cause - Invalid order type was entered And the log contains the following entry (stack dump): JI 09:46:41:713 JTS-EServerSocket-821: Null error type from SCALE JI 09:46:41:714 JTS-EServerSocket-821: [1:37:39:1:0:0:0:ERR] -'ob' : cause - Invalid order type was entered JI 09:46:41:714 JTS-EServerSocket-821: Anticipated error JI jextend.d: Invalid order type was entered at jextend.ob.d(ob.java:671) at jextend.v.h(v.java:227) at jextend.id.H(id.java:657) at jextend.id.run(id.java:531) at java.lang.Thread.run(Unknown Source) I'm on TWS=882.2 and API=9.4. Any insights on what could be causing this, would be much appreciated.