Advice on tax credits and maternity pay

jakesmummy05

I renewed our tax credits in May using the income on P60s. For myself who has been on maternity leave from Jul 2010 until April I deducted £100 per week of maternity pay.
Had award for this year through post this morning and my income was my full income without maternity pay deducted. I have rung them up and they say that the systems they are using this year to cross check incomes isn't showing any maternity pay for me and just my full income.
I have now written a letter to tax credits and sent my P60s with my maternity pay circled plus a covering letter, all by recorded post.
This has meant our tax credits are lower through no fault of mine when they should be a bit higher.

Have I gone about this correctly such as sending the information through post?
Am I correct in thinking you disregard £100 for maternity pay.

Does anyone have an idea on what will happen now and the timescales?

Thanks