Pretty sure it's Heinz's fault because there are loads (if not all) of that have had a 'rebate'. It seems it's because HMRC think we've worked for two companies this year, ............
That would explain it - if HMRC thought Heinz was still your "primary" employment and the "new" company was your second job then they'll have taxed your Heinz income (which was actually zero) at your usual rate and the new company income at a flat rate 22% (if memory serves, or 10%.. I forget which) rather than the usual banded income tax rates.
Then at the end of the year they go "Oh snap, we taxed you too much, have some back!"
ISTR that's basically how it works, anyway, from sorting out my Dad's tax (pension taxed as primary income and a job taxed as secondary meant the tax never worked out right..)
Almost. What happens is everyone is allowed a tax free personal allowance - £9440 last year and £10000 this year. It can be different depending on lots of things, but that's the basic amount. HMRC then issue a Tax Coding notice to all your employers/ sources of income. You primary employer gets the tax code 944 for you. All other employers get a tax code of 000.
The Tax code tells the employer how much your allowance is (divided by 10). So they subtract (one twelth of) that amount from your monthly pay, and then tax you at either 20% or 40% (or 45%) on the remainder. If you don't earn £9440 from the primary employer, then some of your allowance will be left over, and this can be used to reduce your tax from any other employers. Pensions are usually classed as your primary income source.
So for example, if you get £8000 from a pension, and £6000 from some part time extra work. The pension provider will get allocated Tax code 944, so you won't be deducted any tax on that. However, the second employer will probably be allocated tax code 000, meaning that all £6000 will be taxed at 20%, so you'll only receive £4800, and pay £1200 tax. At the end of the year HMRC will (may!) realise that this isn't correct. Your yearly earnings were £14000, of which £9440 is tax free, so you pay 20% on £4560 = £912. So the tax man wil refund £288 (£1200-£912) excess tax you have paid.
PAYE works well for those with one income source, but can be a PITA for those with multiple income sources. It's no wonder many pensioners get in a mess with it when they're getting state pension, several occupational pensions and some part time income.