Holding ISAs after emigrating to Poland

You can keep your ISAs but you can't pay money into them if you move abroad

If you open an Individual Savings Account (ISA) in the UK then move abroad, you cannot put money into it after the tax year that you move (unless you’re a Crown employee working overseas or their spouse or civil partner).

And you must tell the institutions that are managing your ISAs that you've moved abroad. Some institutions don't cater to non-UK customers so it's possible you'd have to move your ISA to an institution that does.

In Poland you could pay into a pension tax free, although there is an annual contribution limit.

expenses related to the taxpayer’s saving for retirement pension – the payments made to the Individual Pension Security Account (indywidualne konto zabezpieczenia emerytalnego, IKZE) made by the taxpayer during the tax year are deductible up to the amount specified in the provisions on the Individual Pension Security Account. Payments made to the IKZE during the calendar year must not exceed the equivalent of 1.2 times the average monthly remuneration forecasted for the national economy for a given year in the Budget Act or in the Act on the Provisional Budget or drafts thereof, if the relevant Act have not been passed. In 2020, the maximum deductible amount is PLN 6,272.40 (ca. EUR 1,442).

There is also an Individual Retirement Account (IKE) scheme in Poland. It's a little more similar to an ISA in that you pay in your post tax income and it's then sheltered from tax but unlike an ISA you can't access that money without penalty till you're at least 55 and you may need to wait till you're 60.