Add whatsnew

Author: kinow

doc/source/whatsnew/v0.25.0.rst

@@ -368,6 +368,8 @@ I/O
 - Improved :meth:`pandas.read_stata` and :class:`pandas.io.stata.StataReader` to read incorrectly formatted 118 format files saved by Stata (:issue:`25960`)
 - Fixed bug in loading objects from S3 that contain ``#`` characters in the URL (:issue:`25945`)
 - Adds ``use_bqstorage_api`` parameter to :func:`read_gbq` to speed up downloads of large data frames. This feature requires version 0.10.0 of the ``pandas-gbq`` library as well as the ``google-cloud-bigquery-storage`` and ``fastavro`` libraries. (:issue:`26104`)
+- Bug in :meth:`DataFrame.to_csv` where values were truncated when the length of ``na_rep`` was shorter than the text input data. (:issue:`25099`)
+-
 
 Plotting
 ^^^^^^^^