No, you can only claim for costs you have already incurred.
If you will be on a long-term placement you can claim part of the costs before the end of the placement if you prefer. For example, if you are on a 2 month placement you can submit a claim for costs from the first month once you have paid them. You can then submit another claim at the end of the placement for the second month.
If you choose to claim in this way make sure you do not claim for overlapping dates.
Both you and your university need to sign and date the form on or after the last date of the placement claim period.