H1B COS 批准并生效后需要做些什么？

看到IRS网站上写"Employers Must Withhold FICA Taxes for Aliens who Change Visa Status to H-1B. Typically, the H-1B change of status becomes effective on October 1st of each year."
那我需要马上更新我的w4 form开始withhold FICA嘛？除此之外我还需要做些什么嘛？如果我晚报了， 是不是当年度的tax return就需要补交错过的FICA了？

Fragomen寄给我的包裹上写道:"U.S. immigration law and regulations require that all foreign nationals, including lawful permanent residents, report each personal change of address and new address with the USCIS with ten days of moving"
所以说，H1B虽然没有F1 OPT Extension 那么繁琐的reporting要求，但还是需要申报住址变化的？