I am a US citizen who worked in Hong Kong for a period. I have since returned to the US and brought a domestic worker back with me and they are here on a B1 visa. My question is two fold. The first is they are waiting on the arrival of their social security number and were unable to obtain an ITIN. Once the social security number is obtained am I required to report the back wages that my employee was paid prior to having the social security number or do I just begin reporting the wages. Also I'm assuming that I am required to pay the OASDI taxes as well as the federal and state unemployment taxes but what taxes is the employee required to pay--they will be here for more than 6 months.

You are required to report all wages that she earned since her arrival.

FICA (Social Security and Medicare) are also due. Those taxes can be paid using Schedule H on YOUR tax return.

Recommend you get local professional help.