In The Unicode Standard, Sinhala script implementation is discussed in  Chapter 13 South and Central Asia-II: Other Modern Scripts.

The Sinhala script was encoded in The Unicode Standard version 3.0. The script is encoded in the following blocks:

BlocksCharacter RangeAdded in Unicode VersionUnicode Chart
Sinhala 0D80..0DFF 3.0  U0D80
Sinhala Archaic Numbers 111E0..111FF 7.0  U111E0

Subsequent to version 3.0, the following characters have been added to the Sinhala script:

CharactersUnicode VersionDocumentation
0DE6..0DEF 7.0  WG2 N3888,  WG2 N3888-a,  WG2 N3888-b,  L2/10-337
111E1..111F4 7.0  WG2 N3888,  WG2 N3888-a,  WG2 N3888-b,  L2/10-337

Documentation refers to  ISO Working Group and Unicode proposals

A number of proposals for its inclusion were submitted to the Unicode Technical Committee and WG2:

1992-11-03 Unicode Technical Report #2 (Sinhala) — Andy Daniels ( Tr2.html)

1996-11-15 Sri Lanka standard Sinhala character code for information interchange — SLS (WG2 N1480 (not online), L2/97-019 (not online))

1997-03-01 Proposal for encoding the Sinhala script in ISO/IEC 10646 (revision 1) — Michael Everson ( (Unofficial HTML version of WG2 N1473), L2/97-018 (not online))

1997-06-13 Mapping of Sinhala from 10646 to SLS 1134 — Michael Everson (WG2 N1589 (not online), L2/97-145 (not online))

1997-07-01 Results of Sinhala ad hoc - Sri Lanka, U.S. Ireland, Unicode (WG2 N1613 (not online), L2/97-158 (not online))

1998-10-23 Part 1:Architecture and Basic Multilingual Plane AMENDMENT 21: Sinhala — WG2 ( WG2 N1896,  WG2 N1896_02n3190_fpdam21_sinhala)

2004-03-09 Indic scripts collation grouping; CTT suggestion — Kent Karlsson ( WG2 2716.doc,  L2/04-109)

2004-04-26 Sri Lanka standard: Sinhala character code for information interchange (SLS 1134:2004 – Draft for Public Comments) — Gihan Dias — ( WG2 N2737,  L2/04-131)

2004-06-07 Comments on draft Sinhala standard (L2/04-131 + L2/04-231) — Eric Muller ( L2/04-235)

2004-06-09 Sinhala Text Representation — Gihan Dias ( L2/04-231)

2004-06-10 Comments on L2/04-235 [Sinhala] — Paul Nelson ( L2/04-239)

2004-06-14 Response to Eric Muller's comments on draft Sinhala standarfd — Gihan Dias ( L2/04-248)

2007-02-08 Proposal to add archaic numbers for Sinhala to the BMP of the UCS — Michael Everson ( WG2 N3195,  L2/07-002)

2008-01-07 Inclusion of archaic Sinhala numerals in the Sinhala character code range — ICT / Sri Lanka ( L2/08-007)

2008-01-28 Archaic Sinhala Numerals — Gihan Dias ( L2/08-068)

2008-02-05 Observations on the Encoding of Archaic Sinhala Numerals in Unicode/UCS — Sri Lanka N.B. ( L2/08-105)

2008-03-02 Criteria for the encoding of script-specific dandas — Unicode and US National Body ( WG2 N3457,  L2/08-118)

2010-05-01 Sinhala Named Sequences — Gihan Dias ( L2/10-164)

2010-05-03 Preliminary Proposal to Encode Sinhala Digits and Numerals — Gihan Dias ( L2/10-165)

2010-08-08 Proposal to add archaic numbers for Sinhala to the BMP and SMP of the UCS — Ireland NB ( WG2 N3876,  L2/10-301)

2010-08-10 Proposal to Encode Sinhala Archaic Numerals and Numbers — Gihan Dias ( L2/10-312)

2010-09-01 Proposal to include Sinhala Numerals to the BMP and SMP of the UCS — SLSI ( WG2 N3888,  WG2 N3888-a,  WG2 N3888-b,  L2/10-337)

2010-10-23 Background information on the use of Sinhala Numerals (L2/10-337) — Harsha Wijayawardhana ( L2/10-433)

2012-07-31 Indic Scripts in Unicode — Eric Muller ( L2/12-289)

2012-11-02 Issues with Sinhala symbols Rakaaraansaya and Yansaya — Gihan Dias ( L2/12-358)

2014-02-05 A bag of suggested improvements to Unicode’s provisional Indic properties — Roozbeh Pournader, Behdad Esfahbod ( L2/14-065)

2014-05-08 Improvements requested for Unicode Indic properties — Roozbeh Pournader ( L2/14-126)