If you fax it, you better have some documentation that reflects the fax went through.
I would recommend you mail it certified mail return receipt requested. This way someone at the IRS signs for it and you know it was actually received.
The taxpayer always has the initial burden of proof and mailing it as reflected above is inexpensive insurance.
Section 7502 of the statute and regulations discusses timely filing of documents and I would recommend you follow those procedures:
Section 7502 provides that, if the requirements of that section are met, a document or payment is deemed to be filed or paid on the date of the postmark stamped on the envelope or other appropriate wrapper (envelope) in which the document or payment was mailed. Thus, if the envelope that contains the document or payment has a timely postmark, the document or payment is considered timely filed or paid even if it is received after the last date, or the last day of the period, prescribed for filing the document or making the payment.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
