IB offers a number of allocation methods, fixed ratio, percent of availability equity, and something else, the name of which I don't recall. Go to the main IB web page. Type in "allocation" in the search function and you will get all the details. Allocation is done at time of trade.
You can set up different account groups. Say you have three accounts that are cash-type such as IRA's Roth's, and your mother's portfolio. You also have your trading account in which you do everything and anything. You can set up the "safe" account as a group and set it to do a 1/3, 1/3, 1/3 allocation of a trade or set it to allocate based on available equity or if you do a fixed share size all the time, say 100, you could set 46, 36, 18.
You can trade against any individual group or all groups. When you want to trade your trading account you set the active account (group) to that group, when trading the safe group and using its allocation method, you select that group.
One problem I have with the auto allocation and sizing is that you have the capability to set a default size (either $ or number of shares/contracts/etc). I like to risk-manage by doing a fixed percent of total account value when entering a position, but IB will not do this automatically. You must compute and manually enter. The default size feature, as currently working, always rounds down to the lower 100 shares when you ask for a Default $ amount. Thus if you have a $5000 default amount and you enter an order to buy XYZ and XYZ is trading at $27 you will buy 100 shares not 200, nor do they compute the number of shares and provide for an odd-lot purchase very close to $5K. Round lots may make a difference in execution in a day trading account but they make little difference in a swing or longer-term account and execution spedd is the only reason I can think of for not allowing odd-lots. Why no rounding up is also beyond me..
Another caveat. IB gives you 100 different data quotes for $10 if you trade less than $30 worth of commissions in a month. If you currently have three accounts, each with 40 positions and you watch some indicators like the S&P, DOW, TRIN, Advance-Decline, etc., you can see them all for "free" as long as you generate $30 in commissions in each account. If you go to a F&F account you will get only 100 data quotes. The same $30 rule covers as many accounts as are in the F&F account. You'll only pay $10 no matter how many accounts. Make the $30 any which way and the fee is waived. However, you cannot get more data until you generate more than $800 in commissions in a month. Then you get one additional data quote per $8 above the $800.
If you open a F&F account with a total of 120 issues in the combo you'll only get 100 quotes. What quotes you get depends on the sequence in which you look at the sub-accounts, if you open the entire F&F account (consolidated account) the quotes appear to be some random show/no show process. If you have an external data feed it obviously will not matter except that you may not see an IB TWS quote when you enter an order. IB may have changed this since I opened my own F&F account, discovered the problem, and took action to fix itl. Then again, they may not have done so.
Jack
