Dishonest mothers help or am I to blame?

The OP has absolutely broken the law here. Do you not realise, OP, that everything you are saying are what a people trafficker/ modern slaver would say?
People can work what hours they choose if they are self employed. If you have ever, once, told her what hours she needs to work for you, you are falling foul of the law, and evading pension and Employer’s Nat Ins.

My cleaner tells me when she is available, charges me what she wants, and brings her own equipment.

An employee at Tesco works when Tesco tells her what her shift is, is paid what Tesco chooses and uses Tesco's equipment to do the work as they instruct her to.

Call HMRC, tell them the terms and conditions the mother's help was working under eg who set the hours, set the wage, provided the equipment, decided how the job was done - they will tell you if she is employed or self employed.

Employment status isn't something the employer or worker just chooses, it's based on the actual job.

I'm pointing this out for a reason, not to be pedantic. You e got gross and net pay the wrong way round. Gross is pre deductions, net is what's left after tax, NI, pension etc. if you've put anything in writing by text for example that you've been paying her net, then yes, she's got a strong case for you needing to now sort out her tax etc on top of that.

You would never agree a net pay amount with a self employed person as it simply doesn't work that way.

You may have inadvertently established her as your employee and as such you are responsible for sick pay, holiday pay, tax etc.

No idea i don't know the ins and out of employment or tax or other relevant laws, if relevant, i guarantee there will be experts on here who do

If you thought she was self employed she should have been providing you with an invoice each week.

If she's your employee did she forward her tax code / P45 on commencement of employment ?

Usually with a mother's help it is employment because the employer sets the hours and terms ie 8-12 or 3-7 etc when they want the help. Whereas with cleaners/gardeners they will say "I can fit you in on Monday at 10 or Thursday at 3" etc,

Usually for self-employed childcare HMRC want you to have 3 clients or that you do a short term contracts - ie maternity nurses that work for 6 weeks and move on to a new client.

And any text / emails of any

conversations / agreements you had from the start.

Is it any different to having a cleaner or a gardener? What is the OP doing wrong, you wouldn't set yourself up as an employer just to have a cleaner

yes - this is the danger for OP

That would likely cause huge problems to OP as it sounds like she is an employee - you can't just choose self employed status unless the mothers' help can choose her hours - so OP could be guilty of non running payroll and not paying employers NI.

Certainly dont send her a payslip, she's not an employee

She's not going anywhere near HMRC, I wouldn't worry about that, tell her you dont need her services any more and be happy you've had a lucky escape

What did you give her tips for OP, that's not a thing for childcarers is it?

Isnt the op doing something against the rules also?

Have I misunderstood that she was claiming to be sick whilst working ft for another family?

Why are you worrying about this. Imagine your working for Tesco's. You agree 25 days holiday and a salary of £20k....then you try to take 30 days and complain to head office you've not been paid £30...they would laugh at you and kick your butt out of the door.

You agreed a price. She's been getting that. Now she wants more. Tell her to jog on... heres the money I owe less the time you were sick... good luck taking any action against me as I'm sure HMRC will be very interested in the fact you never provided your NI number or any details for tax purposes if you thought you were employed

If you have no contract, she has no contract and the verbal agreement is not worth the paper it is written on. Send her a final note on her payslip stating that she herself should be paying her taxes as a self employed person, pay her anything she is owed and tell her you no longer need her services. If she kicks off remind her HMRC will need advising as will the other family she works for.

Cut all ties. She’s far too much trouble already.

I suspect, if you check with HMRC, she is not entitled to be self employed.

Get rid, I wouldn't trust her

Just cut ties with her. If she’s working for another family she’s clearly not your employee - have you got any evidence of this?

Do you have any messages or WhatsApp to back up what you’ve said about self employment?

Just thinking if she does decide to cause trouble with HMRC - but then she shouldn’t do as she is the one working elsewhere!

I'd sack her. Wouldn't have such a sly and dishonest person in my home. She seems work shy anyway so you'll just be speeding up the inevitable.

What does your contract say? I'd stick to that.