Rhode Island General Laws Title 44. Taxation § 44-1-28. Mailing as timely tax filing and payment

(1) Transmitted through the United States mail, is deemed filed and received by the state or political subdivision on the date shown by the post office cancellation mark stamped upon the envelope or other appropriate wrapper containing it;

(2) Mailed but not received by the state or political subdivision or where received and the cancellation mark is illegible, erroneous, or omitted, is deemed filed and received on the date it was mailed if the sender establishes by competent evidence that the report, claim, tax return, statement, remittance, or other document was deposited in the United States mail on or before the date due for filing; and in cases of the non-receipt of a report, tax return, statement, remittance, or other document required by law to be filed, the sender files with the state or political subdivision a duplicate within thirty (30) days after written notification is given to the sender by the state or political subdivision of its non-receipt of the report, tax return, statement, remittance, or other document.