Every conveyancer is legally required to establish where your money came from, not simply that you have it. This is anti-money laundering law rather than any suspicion of you. In practice it means bank statements showing the funds accumulating, plus evidence for anything out of the ordinary such as a gift from family, proceeds of a previous sale or an inheritance. Pulling this together early is one of the simplest ways to avoid a delay, because your file cannot progress until it is complete.