; and (2) the taxes imposed by chapter 2 (other than section 1401(b)) of the Internal Revenue Code of 1986 with respect to self-employment income (as defined in section 1402 of such Code) reported to the Secretary of the Treasury on tax returns under subtitle F of such Code, as determined by the Secretary of the Treasury by applying the applicable rate of tax under such chapter (other than section 1401(b)) to such self-employment income, which self-employment income shall be certified by the Commissioner of Social Security on the basis of the records of self-employment income established and maintained by the Commissioner of Social Security in accordance with such returns. The amounts appropriated by paragraphs (1) and (2) shall be transferred from time to time from the general fund in the Treasury to the Social Security Trust Fund, such amounts to be determined on the basis of estimates by the Secretary of the Treasury of the taxes, specified in paragraphs (1) and (2), paid to or deposited into the Treasury; and proper adjustments shall be made in amounts subsequently transferred to the extent prior estimates were in excess of or were less than the taxes specified in such paragraphs (1) and (2). All amounts transferred to the Social Security Trust Fund under the preceding sentence shall be invested by the Managing Trustee in the same manner and to the same extent as the other assets of the Trust Fund. Notwithstanding the preceding sentence, in any case in which the Secretary of the Treasury determines that the assets of the Trust Fund would otherwise be inadequate to meet the Trust Fund's obligations for any month, the Secretary of the Treasury shall transfer to the Trust Fund on the first day of such month the total amount which would have been transferred to the Trust Fund under this section as in effect on October 1, 1990