How does the new work pension affect the PAS?

My UK occupational pension just started paying out each month, significantly increasing my income. With regard to PAS do I need to do anything to notify the tax authorities before I complete my tax return?

There is nothing specific to do at this stage. Strictly-speaking the PAS only concerns French salaries and French pensions so your UK income sources are outside the scope of this.

Instead, the tax authorities operate an automated direct monthly on-account payment system from your bank account based on your previous tax declaration.

If there is additional tax due on last year’s income due to a new income stream then your avis d’impôt sent out at the end of this summer will indicate what regularisation payments need to be made. 

However, it is usually better to notify the tax office about this new income via your personal space on the tax website when it starts. This can allow you to pay regular instalments and so avoid the inconvenience of regularisation payments.