A taxpayer may make a cash deposit with the Secretary which may be used by the Secretary to pay any tax imposed under subtitle A or B or chapter 41, 42, 43, or 44 which has not been assessed at the time of the deposit. Such a deposit shall be made in such manner as the Secretary shall prescribe.
To the extent that such deposit is used by the Secretary to pay tax, for purposes of section 6601 (relating to interest on underpayments), the tax shall be treated as paid when the deposit is made.
Except in a case where the Secretary determines that collection of tax is in jeopardy, the Secretary shall return to the taxpayer any amount of the deposit (to the extent not used for a payment of tax) which the taxpayer requests in writing.
For purposes of section 6611 (relating to interest on overpayments), except as provided in paragraph (4), a deposit which is returned to a taxpayer shall be treated as a payment of tax for any period to the extent (and only to the extent) attributable to a disputable tax for such period. Under regulations prescribed by the Secretary, rules similar to the rules of section 6611(b)(2) shall apply.
In the case of a taxpayer who has been issued a 30-day letter, the maximum amount of tax under subparagraph (A) shall not be less than the amount of the proposed deficiency specified in such letter.
The term “30-day letter” means the first letter of proposed deficiency which allows the taxpayer an opportunity for administrative review in the Internal Revenue Service Independent Office of Appeals.
Except as otherwise provided by the taxpayer, deposits shall be treated as used for the payment of tax in the order deposited.