Request them before the intended filing period, especially if assets were sold through closed accounts or older records require retrieval. A last-minute bank balance cannot fill a missing history by itself.
Resolve the path before transferring again
Map the existing source and movement of funds, then retain records as additional business payments occur. If several currencies or intermediaries are involved, reconcile them while supporting documents are available. The time needed to complete this record is separate from government processing and appointment availability.
Avoid setting a submission date until important source gaps and the actual commercial commitment can be explained. Request historical records before making any further transfers, because each additional movement lengthens the path that has to be explained and some institutions purge access on their own schedule. Start with anything held by a closed account, a former employer, or an institution in another country, since those are the requests most likely to fail or take months.
Establish what the bank can actually produce and for what period, and obtain complete statements rather than transaction extracts. Where a conversion or a transfer between institutions is planned, document the position before it happens rather than reconstructing it afterwards. Resolving the path first also avoids the common outcome in which money is moved for good commercial reasons and the movement itself becomes the hardest part of the file to explain.