Tax Credits Overpayment/Compliance Help

Hi - first time poster here :j I hope I’m posting in the right place but apologies if not!

I was wondering if somebody could help please. From March 2017-March 2018, I was on maternity leave and my earnings (including the £100pw reduction) was £5839, my partners approximately £27200. When I submitted this on the tax credits renewal, it flagged up as drastically different to my RTI (because of the maternity leave which they wouldn't accept despite being able to see my youngest DOB) and we therefore had a compliance check for every aspect of the claim including the £108pw childcare costs.

Fast forward and I realised that childcare vouchers shouldnt be included so I called them and changed it to £53pw childcare (108-55 vouchers my partner paid).

I went back to work and put my youngest in nursery at a whopping rate of £118pw for my baby and £79 for my eldest (who gets funding) and from 01 June, we stopped the childcare vouchers. I had called TC each time my bills changed (ie when we had 2 children in and then when childcare vouchers stopped).

The compliance team found (after 7/8 weeks and me chasing them!) that my childcare costs should have actually been £27pw because I had actually paid some vouchers at the very beginning of my mat leave and they have said that based on that and my household earnings, we arent eligible for anything 2017/18 year so we owe them the £170 we got awarded last year. When I put it all in the calculator online however, it says we should have been eligible for £72 which cuts the overpayment in half? Its also worth noting that childcare costs fluctuated drastically in 2017/18 due to funding changes so I've requested bank statements to see if I can see how much we paid over to see if that £27 is accurate.

They are also refusing to make any changes to my 2018/19 year so CC costs are still £27 despite no vouchers/2 kids in nursery now. I am contesting this and nursery are providing me with a letter stating costs and when vouchers ended etc. I’m concerned that my eldest stops getting funding in August so it will increase and then starts school in September and therefore childcare costs will reduce again and currently we are having nothing but trouble when costs have remained relatively static.

Can anybody work out what the overpayment actually is approximately? I cant wrap my head around the calculator being so wrong. Also, I have no idea how that overpayment will be worked out.

Its absolutely baffling me tbh and I have no idea what to do other than take them at their word, despite having little faith in them following all the probilens we’ve had. 2017/18 was the first year we have ever asked for/received any help from the Government and it’s been an absolute nightmare and causing too much stress... especially given that currently I have £100pm spare from my wage after childcare and they think I pay £27 :rotfl:

2017/18 earnings - 5839 + 27200
Working week - 37 + 41
Childcare costs - 2 children, pay costs for 1, £27

2018/19 earnings - 14000 + 27500
Working week - 19 + 41
Childcare - 2 children, pay for 2, £27 during April, £145 during May, £197 from June

Payments received 2017/18 - approximately £170 every 4 weeks
Payments received 2018/19 - £270 in April, £90 every 4 weeks, payments stopped end of June.

I still havent received any letters from HMRC despite my claim being stopped at the end of June, however I have put in a complaint about that so any request for overpayment has been put to a halt until its all sorted. 2017/18 through the mandatory reconsideration process (whilst I check bank statements/provide evidence of what their online calculator says) and 2018/19 as another compliance check to prove my costs (although still no letter about this either).

Sorry for the rambling but Im at the end of my tether! My OH keeps telling me to get the MP involved but I don’t know whether thats a little drastic?

Thanks in advance!
Goldilocks