add_expense_refund_modal.php

<div class="modal" id="addExpenseRefundModal<?php echo $expense_id; ?>" tabindex="-1">
  <div class="modal-dialog modal-lg">
    <div class="modal-content bg-dark">
      <div class="modal-header">
        <h5 class="modal-title"><i class="fa fa-fw fa-recycle"></i> Refund</h5>
        <button type="button" class="close text-white" data-dismiss="modal">
          <span>&times;</span>
        </button>
      </div>
      <form action="post.php" method="post" autocomplete="off">
        <div class="modal-body bg-white">
          <input type="hidden" name="account" value="<?php echo $expense_account_id; ?>">
          <input type="hidden" name="vendor" value="<?php echo $expense_vendor_id; ?>">
          <input type="hidden" name="category" value="<?php echo $expense_category_id; ?>">
          
          <div class="form-row"> 
            
            <div class="form-group col-md">
              <label>Refund Date</label>
              <div class="input-group">
                <div class="input-group-prepend">
                  <span class="input-group-text"><i class="fa fa-fw fa-calendar"></i></span>
                </div>
                <input type="date" class="form-control" name="date" value="<?php echo date("Y-m-d"); ?>" required>
              </div>
            </div>
            
            <div class="form-group col-md">
              <label>Refund Amount</label>
              <div class="input-group">
                <div class="input-group-prepend">
                  <span class="input-group-text"><i class="fa fa-fw fa-dollar-sign"></i></span>
                </div>
                <input type="number" class="form-control" step="0.01" name="amount" value="-<?php echo $expense_amount; ?>" required>
              </div>
            </div>
          </div>
          
          <div class="form-group">
            <label>Description</label>
            <textarea class="form-control" rows="4" name="description" placeholder="Enter a description" required>Refund: <?php echo $expense_description; ?></textarea>
          </div>
          
          <div class="form-group">
            <label>Reference</label>
            <div class="input-group">
              <div class="input-group-prepend">
                <span class="input-group-text"><i class="fa fa-fw fa-file-alt"></i></span>
              </div>
              <input type="text" class="form-control" name="reference" placeholder="Enter a reference" value="<?php echo $expense_reference; ?>">
            </div>
          </div>
          
          <div class="form-group">
            <label>Receipt</label>
            <input type="file" class="form-control-file" name="file">
          </div>
          
        </div>
        <div class="modal-footer bg-white">
          <button type="button" class="btn btn-secondary" data-dismiss="modal">Cancel</button>
          <button type="submit" name="add_expense" class="btn btn-primary">Save</button>
        </div>
      </form>
    </div>
  </div>
</div>