Sassy123 they would be reporting fortnightly because they would be in receipt of another payment as well as FTB. You can by all means update your estimate each fortnight but that is really only going to be time consuming. I think you would be best to sit down and look at your income for both yourself and her hubby and really look at your casual income as you don't won't to underestimate as you may end up with an overpayment for your FTB B as that is paid based on the lower income earners income.

The centrelink website has an online estimator I suggest you use that and put in different figures, it will show you what you will receive for your FTB A and B, which will help you see the difference and potential overpayment if you have underestimated.

Obviously if you overestimate when you do your tax at the end of the financial year anything owed to you will be topped up.