Before. Retrieval times are outside your control: registries, former counterparties and banks all move at their own pace. Learning that a settlement statement from an older sale is unavailable is far cheaper before capital is committed than after a petition is prepared around it.
Sequencing document recovery against the stages ahead
The case has stages: the petition, visa availability, then an immigrant visa or an adjustment you are genuinely eligible for, then conditional residence, and ordinarily an I-829 filed during the 90-day period immediately before the second anniversary. Missing donor records slow the first stage and echo through the rest. Note also that filing alone confers no work or travel permission.
An applicant who has not yet sold the house cannot show the capital, and a pension election that is merely intended does not exist as a source.
Identify which forecast or document needs updating and who provides the revised information. Source-of-funds review under the current rules is not limited to the capital actually contributed to the enterprise; documentation may also be required for administrative costs and fees connected with the case and, where relevant, for anyone who transferred funds toward the investment. A sibling handling an old sale is one link in that chain, and the chain can extend further back than a single transaction if the proceeds passed through several hands before reaching the investor. Ask an adviser to map every transfer in the path rather than stopping once the most recent document is located. Older records tend to degrade or disappear faster than recent ones, so identifying every link early leaves more time to replace whatever cannot be recovered.