When I transform xml into xhtml using my code below, it leaves a carriage return between the opening and closing <input> tags:

XSLT:

<input type="radio" name="abc">
  <xsl:attribute name="value">
    <xsl:value-of select="@ActivityCode"/>
  </xsl:attribute>
  <xsl:attribute name="id">
    <xsl:value-of select="@ActivityCode"/>
  </xsl:attribute>
</input>
<label>
  <xsl:attribute name="for">
    <xsl:value-of select="@ActivityCode"/>
  </xsl:attribute>
  <xsl:value-of select="@ProgramName"/>
</label>

XHTML Rendered:

<input type="radio" name="abc" value="a1" id="a1">
</input>
<label for="a1">111</label>
<br />
<input type="radio" name="abc" value="a2" id="a2">
</input>
<label for="a2">222</label>
<br />
etc...

Ideally I want to get rid of the closing input tag and make it a self-closing input tag like this: <input />. But this doesn't seem to be doable, so I want to at least get rid of the carriage return to be valid xhtml. Does anyone know how to do this?

XSLT 2.0 has an output method="xhtml".

You don't say what output method you are using or which XSLT version you are using.

Also, your output appears to have a single space as the content of the input element, but there's nothing in your stylesheet that could produce that space.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

I'm using XSLT 1.0. My output method is XML but I'm producing XHTML:

<xsl:output omit-xml-declaration="yes" method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

Can I still generate the valid <input> with XSLT 1.0?

If you're stuck with XSLT 1.0 then my advice would be to produce two different serializations of the output: an HTML serialization for sending to the browser, and an XML serialization for sending to anyone else. There are no mechanisms in XSLT 1.0 to serialize using the special compromise conventions defined in the XHTML specification, for example forcing an empty paragraph to be output as <p></p>.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Which XSLT processor do you use? I could imagine that you get
  <input ...></input>
or
  <input/>
both of which are not good for XHTML sent to text/html browsers but I don't understand why you would get
  <input ...>
  </input>
unless there is something wrong with the indentation/serialization.