SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 13G*
                                 (Rule 13d-102)

                           INFORMATION TO BE INCLUDED
                          IN STATEMENTS FILED PURSUANT
                           TO RULES 13d-1(b), (c), AND
                           (d) AND AMENDMENTS THERETO
                          FILED PURSUANT TO RULE 13d-2
                                (AMENDMENT NO. )*

                           Nuveen Senior Income Fund
--------------------------------------------------------------------------------
                                (Name of Issuer)

                       Variable Rate Term Preferred Shares
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                  67067Y-60-9
            --------------------------------------------------------
                                 (CUSIP Number)

                                December 30, 2013
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

   /X/       Rule 13d-1(b)
   / /       Rule 13d-1(c)
   / /       Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which
would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section
of the Act but shall be subject to all other provisions of the Act (however,
see the Notes).

                                      Page 1
                                    of 9 Pages



                                       13G

CUSIP NO. 67067Y-60-9                                         Page 2 of 9 Pages

-------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS


     CRC Funding, LLC
-------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

                                                                       (a)  / /
                                                                       (b)  / /
-------------------------------------------------------------------------------
 (3) SEC USE ONLY


-------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION                              Delaware


-------------------------------------------------------------------------------
       NUMBER OF           (5) SOLE VOTING POWER

        SHARES
                           ----------------------------------------------------
     BENEFICIALLY          (6) SHARED VOTING POWER                          580

       OWNED BY
                           ----------------------------------------------------
        EACH               (7) SOLE DISPOSITIVE POWER                       580

      REPORTING
                           ----------------------------------------------------
       PERSON              (8) SHARED DISPOSITIVE POWER

        WITH:
-------------------------------------------------------------------------------
(9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON            580



-------------------------------------------------------------------------------
(10) CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
     INSTRUCTIONS)  / /


-------------------------------------------------------------------------------
(11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)                     100%



-------------------------------------------------------------------------------
(12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)                             OO



-------------------------------------------------------------------------------



                                      13G

CUSIP NO. 67067Y-60-9                                         Page 3 of 9 Pages


-------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS


     Citibank, N.A.
-------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

                                                                       (a)  / /
                                                                       (b)  / /
-------------------------------------------------------------------------------
 (3) SEC USE ONLY


-------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION                              Delaware


-------------------------------------------------------------------------------
       NUMBER OF           (5) SOLE VOTING POWER

        SHARES
                           ----------------------------------------------------
     BENEFICIALLY          (6) SHARED VOTING POWER                          580

       OWNED BY
                           ----------------------------------------------------
        EACH               (7) SOLE DISPOSITIVE POWER                       580

      REPORTING
                           ----------------------------------------------------
       PERSON              (8) SHARED DISPOSITIVE POWER

        WITH:
-------------------------------------------------------------------------------
(9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON            580

-------------------------------------------------------------------------------
(10) CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
     INSTRUCTIONS)  / /


-------------------------------------------------------------------------------
(11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)                     100%


-------------------------------------------------------------------------------
(12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)                             BK


-------------------------------------------------------------------------------



                                      13G

CUSIP NO. 67067Y-60-9                                         Page 4 of 9 Pages


-------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS


     Citicorp
-------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

                                                                       (a)  / /
                                                                       (b)  / /
-------------------------------------------------------------------------------
 (3) SEC USE ONLY


-------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION                              Delaware


-------------------------------------------------------------------------------
       NUMBER OF           (5) SOLE VOTING POWER

        SHARES
                           ----------------------------------------------------
     BENEFICIALLY          (6) SHARED VOTING POWER                          580

       OWNED BY
                           ----------------------------------------------------
        EACH               (7) SOLE DISPOSITIVE POWER                       580

      REPORTING
                           ----------------------------------------------------
       PERSON              (8) SHARED DISPOSITIVE POWER

        WITH:
-------------------------------------------------------------------------------
(9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON            580


-------------------------------------------------------------------------------
(10) CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
     INSTRUCTIONS)  / /


-------------------------------------------------------------------------------
(11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)                     100%


-------------------------------------------------------------------------------
(12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)                             HC


-------------------------------------------------------------------------------




                                       13G

CUSIP NO. 67067Y-60-9                                         Page 5 of 9 Pages


-------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS


     Citigroup Inc.
-------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

                                                                       (a)  / /
                                                                       (b)  / /
-------------------------------------------------------------------------------
 (3) SEC USE ONLY


-------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION                              Delaware


-------------------------------------------------------------------------------
       NUMBER OF           (5) SOLE VOTING POWER

        SHARES
                           ----------------------------------------------------
     BENEFICIALLY          (6) SHARED VOTING POWER                         580*

       OWNED BY
                           ----------------------------------------------------
        EACH               (7) SOLE DISPOSITIVE POWER                      580*

      REPORTING
                           ----------------------------------------------------
       PERSON              (8) SHARED DISPOSITIVE POWER

        WITH:
-------------------------------------------------------------------------------
(9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON           580*



-------------------------------------------------------------------------------
(10) CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
     INSTRUCTIONS)  / /


-------------------------------------------------------------------------------
(11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)                    100%*



-------------------------------------------------------------------------------
(12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)                             HC


-------------------------------------------------------------------------------
* Includes shares held by the other reporting persons.



Item 1(a).     Name of Issuer:

               Nuveen Senior Income Fund

Item 1(b).     Address of Issuer's Principal Executive Offices:

               333 West Wacker Drive
               Chicago, IL 60606

Item 2(a).     Name of Person Filing:

               CRC Funding, LLC ("CRC Funding")
               Citibank, N.A. ("Citibank")
               Citicorp
               Citigroup Inc. ("Citigroup")

Item 2(b).     Address of Principal Business Office or, if none, Residence:

               The address of the principal business office of CRC Funding is:

               70 Washington Boulevard
               Stanford, CT 06901

               The address of the principal business office of Citibank,
               Citicorp and Citigroup is:

               399 Park Avenue
               New York, NY 10022

Item 2(c).     Citizenship:

               CRC Funding is a Delaware limited liability corporation.

               Citibank is a national banking association.

               Citicorp and Citigroup are Delaware corporations.

Item 2(d).     Title of Class of Securities:

               Variable Rate Term Preferred Shares

Item 2(e).     CUSIP Number:

               67067Y-60-9


                                       Page 6
                                     of 9 Pages


Item 3.      If This Statement Is Filed Pursuant to Sections 240.13d-1(b) or
             240.13d-2(b) or (c), Check Whether the Person Filing Is a(n):

             (a)  [ ] Broker or dealer registered under Section 15 of the
                      Act (15 U.S.C. 78o);

             (b)  [X] Bank as defined in Section 3(a)(6) of the Act
                      (15 U.S.C. 78c);

             (c)  [ ] Insurance company as defined in Section 3(a)(19) of
                      the Act (15 U.S.C. 78c);

             (d)  [ ] Investment company registered under Section 8 of the
                      Investment Company Act of 1940 (15 U.S.C. 80a-8);

             (e)  [ ] Investment adviser in accordance with Section
                      240.13d-1(b)(1)(ii)(E);

             (f)  [ ] Employee benefit plan or endowment fund in accordance
                      with Section 240.13d-1(b)(1)(ii)(F);

             (g)  [X] Parent holding company or control person in accordance
                      with Section 240.13d-1(b)(1)(ii)(G);

             (h)  [ ] Savings association as defined in Section 3(b) of the
                      Federal Deposit Insurance Act (12 U.S.C. 1813);

             (i)  [ ] Church plan that is excluded from the definition of an
                      investment company under Section 3(c)(14) of the
                      Investment Company Act of 1940 (15 U.S.C. 80a-3);

             (j)  [ ] A non-U.S. institution in accordance with Section
                      240.13d-1(b)(1)(ii)(J);

             (k)  [ ] Group, in accordance with Section 240.13d-1(b)(1)(ii)(K).
                      If filing as a non-U.S. institution in accordance with
                      Section 240.13d-1(b)(1)(ii)(J), please specify the type
                      of institution: ____________________________ .


Item 4.   Ownership. (as of December 30, 2013)

          (a)  Amount beneficially owned: See item 9 of cover pages

          (b)  Percent of class: See item 11 of cover pages

          (c)  Number of shares as to which the person has:

                  (i)   Sole power to vote or to direct the vote:

                  (ii)  Shared power to vote or to direct the vote:

                  (iii) Sole power to dispose or to direct the disposition of:

                  (iv)  Shared power to dispose or to direct the disposition of:


                  See Items 5-8 of cover pages


                                       Page 7
                                     of 9 Pages


Item 5.   Ownership of Five Percent or Less of a Class.

          If this statement is being filed to report the fact that as of the
          date hereof the reporting person has ceased to be the beneficial owner
          of more than five percent of the class of securities, check the
          following [  ].

Item 6.   Ownership of More Than Five Percent on Behalf of Another Person.

          Not Applicable.

Item 7.   Identification and Classification of the Subsidiary Which Acquired
          the Security Being Reported on by the Parent Holding Company.

          CRC Funding is a partially supported multi-seller commercial paper
          conduit sponsored by Citibank. Citicorp is the sole stockholder of
          Citibank. Citigroup is the sole stockholder of Citicorp.

Item 8.   Identification and Classification of Members of the Group.

          Not Applicable.

Item 9.   Notice of Dissolution of Group.

          Not Applicable.


                                       Page 8
                                     of 9 Pages



Item 10.  Certification.

     By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired and are held in the ordinary
course of business and were not acquired and are not held for the purpose of or
with the effect of changing or influencing the control of the issuer of the
securities and were not acquired and are not held in connection with or as a
participant in any transaction having that purpose or effect.


SIGNATURE.

          After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement is true,
complete and correct.

Dated: January 7, 2014


                      CRC FUNDING, LLC

                      By: Citibank, N.A., as Attorney-in-Fact


                      By: /s/ John Siris
                         --------------------------------------------
                         Name:   John Siris
                         Title:  Vice President


                      CITIBANK, N.A.


                      By: /s/ Ali L. Karshan
                         --------------------------------------------
                         Name:   Ali L. Karshan
                         Title:  Assistant Secretary


                      CITICORP


                      By: /s/ Ali L. Karshan
                         --------------------------------------------
                         Name:  Ali L. Karshan
                         Title: Assistant Secretary


                      CITIGROUP INC.


                      By: /s/ Ali L. Karshan
                         --------------------------------------------
                         Name:   Ali L. Karshan
                         Title:  Assistant Secretary

                                 Page 9
                               of 9 Pages

                          EXHIBIT INDEX TO SCHEDULE 13G
                          -----------------------------

EXHIBIT 1
---------

Agreement among CRC Funding, Citibank, Citicorp and Citigroup as to joint filing
of Schedule 13G