Difference in carry forward losses as computed u/s 143(1) and by the taxpayer

ITR filed for one person has been processed with no demand/refund. Carry forward losses calculated by tax department is significantly lower than calculated by taxpayer. C/f loss as provided by taxpayer is more than 1 crore, while c/f loss as per IT department is only around 55 lakhs. How to find out the discrepancy. C/f losses included loss in sale of foreign shares as well. Is it rejected? Please let me know how to resolve this issue?