diff --git a/RELEASES.md b/RELEASES.md
index 96f9641a9..d4464d07c 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -4,6 +4,25 @@ Go [here](https://github.com/open-source-economics/Tax-Calculator/pulls?q=is%3Ap
for a complete commit history.
+2018-09-11 Release 0.21.0 : FIRST RELEASE COMPATIBLE ONLY WITH PYTHON 3.6
+-------------------------------------------------------------------------
+(last merged pull request is
+[#2058](https://github.com/open-source-economics/Tax-Calculator/pull/2058))
+
+**API Changes**
+- Require Python 3.6 to run Tax-Calculator source code or conda package
+ [[#2058](https://github.com/open-source-economics/Tax-Calculator/pull/2058)
+ by Martin Holmer], which requires new `puf.csv` input file (see [taxdata pull request 283](https://github.com/open-source-economics/taxdata/pull/283) for details) with this information:
+ * Byte size: 56415698
+ * MD5 checksum: 3f1c7c2b16b6394a9148779db992bed1
+
+**New Features**
+- None
+
+**Bug Fixes**
+- None
+
+
2018-09-06 Release 0.20.3 : LAST RELEASE COMPATIBLE WITH PYTHON 2.7
-------------------------------------------------------------------
(last merged pull request is
diff --git a/conda.recipe/meta.yaml b/conda.recipe/meta.yaml
index bf4e26502..97651e7da 100755
--- a/conda.recipe/meta.yaml
+++ b/conda.recipe/meta.yaml
@@ -8,7 +8,7 @@ build:
requirements:
build:
- - python >=3.6.5
+ - python >=3.6.5,<3.7
- numpy >=1.12.1
- pandas >=0.22.0
- bokeh >=0.12.3
@@ -16,7 +16,7 @@ requirements:
- toolz
run:
- - python >=3.6.5
+ - python >=3.6.5,<3.7
- numpy >=1.12.1
- pandas >=0.22.0
- bokeh >=0.12.3
diff --git a/docs/index.html b/docs/index.html
index ac7741747..b82d3ab0f 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -41,6 +41,11 @@ What's New
than an older version that your browser has saved in its cache of
previously visited pages.
+Code changes so works only with
+Python 3.6 plus minor PUF data change are available in Tax-Calculator
+release 0.21.0 and higher. Note that release 0.21.0 is the first
+release that is compatible with only Python 3.6.
+
Both CPS and PUF data improvements
are available in Tax-Calculator release 0.20.3 and higher.
Note that release 0.20.3 is the last release that will be compatible
diff --git a/docs/index.htmx b/docs/index.htmx
index cb7bbb440..88bfb60dc 100644
--- a/docs/index.htmx
+++ b/docs/index.htmx
@@ -40,6 +40,11 @@ ensure you are viewing the most recent version of this page rather
than an older version that your browser has saved in its cache of
previously visited pages.
+Code changes so works only with
+Python 3.6 plus minor PUF data change are available in Tax-Calculator
+release 0.21.0 and higher. Note that release 0.21.0 is the first
+release that is compatible with only Python 3.6.
+
Both CPS and PUF data improvements
are available in Tax-Calculator release 0.20.3 and higher.
Note that release 0.20.3 is the last release that will be compatible
diff --git a/docs/recipe00.graph.html b/docs/recipe00.graph.html
index e8f3bb2c0..047103d1c 100644
--- a/docs/recipe00.graph.html
+++ b/docs/recipe00.graph.html
@@ -15,11 +15,11 @@
-