Tax credits calculator wrong??

Hey there,

I am currently on maternity leave and only get smp. Handily my daughter was born on the very last day of the tax year so virtually all of my mat leave will fall into the same tax year. It's my first child so first time claiming.

So I put my details into the HMRC tax credits calculator, taking into account the first £100 a week of my mat pay (which is 33 weeks of the year) isn't considered, plus my predicted earnings when I go back part time in January, which comes to £3700. My partner earns £15,200 so according to the calculator we are entitled to just under £3000 which works out at around £40 a week.

We haven't received the paperwork back yet (I did a claim based on last years earnings and was entitled to no award as expected so now I have called them and told them about my decrease in earnings and gave them my predicted earnings of £3700). So in total we earn £18,900. The figure the calculator gave us matches what the entitlement table also states.

So why have I recieved only £4.83 in my bank today from them? (Bear in mind I am still awaiting paperwork telling me what my award is).