This section of the novel comes in Chapter 54, which narrates how, in spite of Pip's best efforts, Magwitch is captured by the crown. What is key to note in this chapter is how Magwitch's capture changes Pip's feelings towards his benefactor, and how he very kindly keeps the loss of his fortune away from Magwitch, so he dies under the illusion that he has succeeded in his aim of "making" a gentleman. The passage where Pip reveals his loss of wealth goes as follows:
No. I had thought about that while we had been there side by side. No. Apart from any inclinations of my own, I understood Wemmick's hint now. I foresaw that, being convicted, his possessions would be forfeited to the Crown.
Thus with the capture of Magwitch and his state as prisoner, the Crown (or government of England) seizes all of his assets and wealth, meaning that Pip is not left with any money. So, a sad truth, but what is more important to focus on in this chapter is how Pip matures and develops through his loss of money, and also how he comes to care for Magwitch as a kind of father-figure.