In my ISA account how do I know which year it relates to

[shanghaiscouse]

OK so in my ISA account I have ISAs for 2 years that I created directly with IG during that ISA year, but I have also just started to transfer a previous year ISA across.  I had £37k balance (thanks to coronavirus) for 2 years (original investment of 2x20k=40k) being 18/19 and 20/21 and now I have also transferred my prior year 17/18 ISA from Funding Circle, but as that takes time to liquidate then as a first step to get the whole thing set up I could only transfer across the liquid part i.e. £2k.  So now I have £37+£2 = £39k in my IG ISA.  But how do I know that IG knows that £2k relates to 17/18, 20k to 18/19 and 20k to 19/20?  I am concerned that nobody knows that the £2k relates to 17/18 as I cannot see anywhere in the account information what tax year each ISA contribution relates to.