On or before 31st October 2018 those in the self-assessment system must submit their 2017 personal tax return (declaration of income and capital gains) and pay their income tax balance for 2017, while also making a preliminary tax payment for 2018
Your last chance of reducing your income tax bill for 2017 is by making a pension contribution
You have the choice to claim relief against your income for 2018 (the year of the payment) or against your income for 2017 which will back-date the relief. Relief on the following contributions can be backdated;
The ROS deadline is 14th November 2018 and this should also be relevant to pensions contributions.