If you claim a refund for an excess, then you must be able to prove with documentation that an excess was in fact, withheld. You can calculate all you want, but how are you going to prove that your calculated amount was the amount actually withheld? You cannot guess that the employer did it correctly or withheld an excess, you must have some kind of employer provided documentation that they did. Without either a W-2 or pay stubs you would have a difficult time proving that the employer withheld *any* CASDI at all.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
