Yes, but you may have to wait longer to receive your tax rebate.
You can claim a tax rebate if HMRC's records show that you paid too much income tax. Missing a P45 is not ideal, as this means that we would have to rely on the UK tax office's records about your employment to calculate if you qualify for a tax rebate. A P45 stipulates how much tax you paid during the course of your employment, as well as other important info regarding your tax position when you left your job (like your tax code, etc.). If HMRC's records about your employment turned out to be inexact, the only way we could disprove it would be with presenting them with a P45 for that particular employment. Not being able to show a P45 as supporting evidence means that we would have to accept HMRC's records regarding your employment as exact. Missing the P45 from your last employer in the UK is more problematic, especially if you are trying to make an "in-year" tax rebate claim (meaning you are trying to reclaim tax overpayments from the amount of income tax you paid in this current tax year, 2015/16). HMRC may very well turn down your claim if you don't supply Part 2 and Part 3 of the P45 from your last employer in the UK. If this is the case, you could still submit your claim after the end of the tax year (after 5th April 2016). In some cases, and at their sole discretion, HMRC may accept a Statement of Earnings in place of a P45. If you are leaving the UK and are missing your last P45, get in touch with one of our experts so we can advise you further about how to obtain a Statement of Earnings.