The concessional contributions cap generally includes any contribution for which a tax deduction has been claimed.
For 2019/20 the standard concessional contributions limit is $25,000 regardless of age. This limit is subject to indexation but may not increase each year.
If you exceed the concessional contribution cap then 85% of excess contributions can be refunded and is taxed at your marginal tax rate including levies (less the 15% tax already paid). Tax penalties may apply. If the excess is not refunded it will also count against the non-concessional contribution cap.
Please note: Since 1 July 2018, a new carry forward provision applies for concessional contribution caps. This means that any unused portions of your concessional contribution caps can now be carried forward for up to five years as long as your total superannuation balance does not exceed $500,000. Once you exceed this threshold, the carry forward provision will no longer be available for you to use, however the $25,000 concessional contribution cap will still apply. The first year you will be entitled to carry forward unused amounts is the 2019-20 financial year. This will be beneficial for those who take career breaks or have lumpy income.