2 jobs- does it matter which one is classed as main job (tax purposes)

[tid2018]

Hi all,
Hoping someone can help. I have looked on hmrc website but it's as clear as mud!
I gave recently finished a PhD due to start work soon ( so have been unemployed and not paid taxes for 3 years). I have acquired 2 jobs in 2 large organisations. Both 18.5 hours per week.
Job 1 due to start next week. This job pays 2k less per year (pro rata'd) than job 2
Job 2 due to start in September

As I am likely to get paid from job 1 first ( due to earlier start date) will this automatically be classed as main job? My understanding is that I am better off financially my main job being my higher paid job (due to tax personal allowance) which would be job 2. Also I have student loan re-payments, again in terms of which is most beneficial for me does it matter which salary pot I pay this from?
Thanks in advance!

The way I understand it- have 2 jobs- is it is better to have full allocation to highest paying job as it means you get full benefit of pension contributions. This is if employer is contributing obviously as it means they will contribute more as your contribution is higher iyswim. This may just be my situation as I don't pay pension contributions on my second post so might not make sense for you.

There is no such thing as a "main job". You can choose how your personal tax allowance is split - you can have it to your first job, second job or split it between both - just phone HMRC and tell them what you want to do with it. Your tax code has no bearing whatsoever on anything else - it doesn't affect pension contributions, NIC contributions nor student loan payments - all those are worked out completely separately from your tax code.

If both jobs are paid similarly then probably best to halve it so half your tax code is applied to each job - assuming that you earn at least £6k p.a. from each job. If one of your jobs pays less, then it needs less of your tax code.

If your total pay from both jobs will breach the higher rate threshold of £47k, then things are a lot more complicated and you'd need to tell HMRC of the estimated earnings from both jobs so that they can do a coding adjustment to collect some tax at higher rate from the higher paying job.