Can I take a 2nd (part time) job without telling 1st employer?

[Happening]

I am currently employed by existing employer for 1 day (7.5 hours) per week. Potentially (this is very hypothetical as I've not been offered the job yet!) about to take on a new job of probably up to 20 hours / week.

I would be quitting old job to do new job. However, for reasons that probably aren't relevant here, will need to start the new job a couple of months before I can hand my notice in at my old job.

There is nothing in my contract preventing me from working elsewhere. So I don't think I am obliged to tell my employer?

Will my tax code be changed and would this flag up to my employer I am working in a 2nd job?

If there is nothing in your contract to say that you can't, then no.

for 7.5 hours/week, I wouldn't have thought they'd be surprised if you did anyway though!

Normally, your tax code for your 2nd job would change, not for your first - also it can take HMRC a while to get up to speed; and your tax code could change for many reasons, which your 1st employer wouldn't be told about anyway - they just get a notification of what your new code it.

It's a possibility your old employer might find out you have a second job through tax but probably not after just two months. If you get the job would it not be better just to mention it because you might need the first employer for a reference at some time in the future. But it's difficult if you don't want to hand in your notice right away but wait for two months. Not sure what I'd do in your case. But I agree that your one day a week employer can hardly be surprised that you want more hours.

Ellypoo, not exactly these days. I suspect Hmrc will change tax code after one round of pay from each and it will be divided by expected income of the two iyswim.

So 7.5 hrs job will (if my assumption is correct) pay considerably less than the 20 hr job and tax code will be adjusted accordingly.

For instance £10 p/h in first job will only gross £3900 pa, or 1/3 of annual persoanl allowance so tax code will be reduced to approx 350L or therabouts.

Yes OP your tax code will most likely change and they do it quickly these days with the advent of real time reporting oh the joys of payroll

It's also true that an employment of 7.5 hrs per week has no right to demand/care that you work elsewhere at the same time (caveat - contractual clauses permitting etc)

Fair enough thegirl.

However my very recent experience with HMRC is that they really aren't on the ball with adjustments and tax code changes at the moment, especially since the introduction of RTI (when you would think that things would speed up somewhat!!!).

I agree it can be hit and miss, but nevertheless it is possible (and it is the purpose of RTI) to have tax code adjustments made within hours of an RTI submission as I found to my cost recently!

I'm a payroll agent as part of my work and after we changed software, put all 350 employees from one particular co. onto new software and made submissions - all 350 tax codes were split by the next morning meaning about 2 hours on the phone for our lovely office junior. Thats before the confused phone calls from the employees started coming through a day or two later.... grrr!

Oh and we hadn't switched software providers, just upgraded our system to handle more employees per company.

Hmrc in efficency at it's best