If you are eligible for an SSN and have applied, wait to file your tax returns until it arrives, even if you are late. There is no late fee if you are due a refund. The late fee if you owe tax is a percentage of what you owe, so to reduce your penalty, you should make an estimated tax payment as soon as you can at www.irs.gov/payments. You will get credit for the estimated payment on your tax return. Then, if you do get a bill for a late fee, you can request a waiver (abatement) for good cause.