Calculating tax on salary drop half way through year

[Hairybaker]

I am currently on £80k. I have accepted a new job that better suits my work life balance that is £50k. How can I calculate my monthly take home salary on this new job for the rest of the tax year given that for 4 months of this financial year I have been paid the higher salary?!
Am I being a bit thick!?

You'll be on the same tax rate?

I did say I was being thick 🤣

Very rough calculation:
£80,000 /12 x 4
£50,000 /12 x 8
= annual gross salary

Do the same calculation for for NI, pension contributions, student loans etc and deduct from gross salary = annual taxable pay. Use this calculator to work them out for £50,000 www.moneysavingexpert.com/tax-calculator/

From the annual taxable pay
Deduct £12,500 tax free allowance
Deduct £37,700 20% tax rate and work out 20% = £7,540
Work out 40% of the remainder.

This gives you total tax due for the year. Deduct the tax already paid from this and divide by 8 to get new monthly tax rate. Deduct this from your new gross monthly salary along with NI, pension contributions etc.