End of tax year question?

Will the tax office get any information about my P60 before I send it to them if I want a tax rebate?

Also, I think they may have my start date wrong for my current employer... will that cause any problems?

No. The employer has six weeks to send in his employer's returns after 5th April, and then they have to be processed. The National Insurance Office imput the form P14 (HMRC copy 0f P60) into the computer system, and that takes forever.
Employers' PAYE returns have now been centralised, so local tax offices don't have access to the actual forms. Although now employers do it on-line, so that may cut down time.
Send your form P60 to HMRC and ask for computation. Otherwise you may have to wait until the autumn/winter.

Your employer legally has to send your P60 details to HM Revenue and Customs by 19th May. The employer form is called a P35. They also have to give you your P60 within a certain time frame, I think before the end of June. So it really depends on who they send what first.

I'm not sure why this would be a problem though, if you intend to send it to them anyway. Also, I wouldn't worry about it too much because there is currently a 2 year delay of when HMRC receive your employer's P35 and when they finally check it as a matter of routine!

As for start dates, this doesn't really matter provided the information they receive contains all of your taxable earnings and tax paid. Whether they think you started on the 1st and got paid on the 5th, and you actually started on the 4th and got paid on the 5th will not matter, provided you tell them the amount you got paid etc.

I strongly advise you give your tax office a call. Ask your employer for their tax reference and tax office contact details. People think HMRC are money grabbers, but they are really helpful and will actually give you very good advice to help you avoid taxes!

Good luck.