I am a UK citizen on an H1B visa, employed at a US university. Both payroll and the International Office determined that I was eligible to claim a tax treaty exemption, and I have been exempt from Federal and State taxes since November 2007. I recently got my Green Card (through marriage to a US citizen). My question is do I have to start paying full taxes now or can I wait until the beginning of the new tax year (next year)?

This is really a tax question, not immigration.

As an H-1B you are a nonimmigrant and clearly able to take advantage of certain treaties, as a permanent resident you are a US national and required to pay taxes on income. Please confirm this with an experienced CPA.

If this was helpful, please rate this answer! Good luck.

I wanted to reiterate the following. I fully understand that I need to pay taxes. My question is do I have to start paying full taxes right away or can I wait until the beginning of the new tax year (next year)? In other words, will the taxes have to be deducted from my next pay check? I cannot afford this at the moment and if it is acceptable to pay the tax as a lump sum at the end of the tax year, I would prefer this option. Please advise. Thanks in advance.

I really don't know much about tax law. What I do know is if you have tax liability as a permanent resident, even for a short period, that tax should be paid in the tax year it was incurred.

Please consult with an experienced CPA, I'm really limited to US immigration. Good luck congratulations on your US permanent residence!