I also wanted to ask about what might happen cos we made the appeal 45 days after the date of refusal of the application.will they backdate our payment?(The application itself was made a within the 3 month of the child birth)
You always have up to 30 days to submit an appeal against a letter of rejection of a Tax Credits claim. But the Tax Credits office have the ability to accept a late appeal, as long as it is made before one year is up. If they are not minded to accept the late appeal, well that question can be tested before the Tribunal.
But if they accept the late appeal, it is as if the appeal had been made in time. And from what you have posted, it sounds like they have indeed accepted the late appeal, in which case the claim should be back-dated, as relevant, to up to three months before the date of claim.
...... the tax credit office has paid some amount in her account(tax credit payment).we do not know wich one was paid (child tax or working tax credit).
It could of course be both WTC and CTC. Ordinarily both are paid together, as relevant.