Vetting is a background examination rather than a documentary formality, and complete candour about immigration history matters more than presentation. Prior refusals, withdrawn applications, periods of unlawful presence, criminal records and the origin of the funds being paid are the kinds of matters that must be disclosed accurately, because a concealment discovered later is worse than the fact concealed.
A prior refusal is a fact to explain, not a fact to hide
Applicants who have been refused something in the past often assume the refusal is disqualifying and are tempted to leave it out. Non-disclosure creates a second and more serious problem, because a misrepresentation on a material point has consequences of its own that reach far beyond the application in hand. Hypothetical example: an applicant from Sainte-Cécile-de-Milton was refused a visitor visa many years ago on grounds she never fully understood, and no longer holds the paperwork.
The right course is to reconstruct the record, obtain what can be obtained from official sources, and put forward an accurate account with an explanation. Assembling the funds record early is equally sensible, since a payment of this size will be examined for its origin whatever the framework's own terms say, and a bank that cannot explain an inbound transfer will freeze it long before any official does.