also: ことしちゅうに
expression, adverb
by the end of this year; within this year
Used to set a deadline or express that something will happen before the current year ends. The reading ことしじゅうに is more common than ことしちゅうに.
今年中に引っ越す予定です。
I plan to move by the end of this year.
今年中にこの仕事を終わらせなければならない。
I have to finish this work within this year.
年内に also means 'within the year', but is slightly more formal and can refer to any year from context, while 今年中に explicitly means 'this year'.
Compound of 今年 (this year) + 中 (within) + に (particle). The reading じゅう is the standard kun'yomi-based reading for 中 in this temporal sense; ちゅう is an alternative on'yomi reading.