If you mean, can you decode the entire contents of the QR code, even if part of the code is obscured or changed, then yes you can - sometimes.
QR codes can be encoded with various levels of redundancy, which are known as levels L, M, Q and H and correspond to redundancies of the order of 7%, 15%, 25% and 30%. This means that you can lose most of the barcode and still decode it. The more you lose, the more difficult it is to decode, but it remains possible within these limits.
Please note that some areas of the QR code cannot be lost. You must find the finder (squares in the corners); they can tolerate some distortion, but there are no errors to correct. In addition, the regions around the crawler patterns encode the format and version. They have different redundancy (2x encoding using BCH, not Reed-Solomon), but if you lose too many of those tiny areas that you cannot decode, regardless of the main error.