Self employed and "free" childcare

This might be a bit niche but wondering if anyone can answer this.

I went self employed last year. First the first 12 months they relax the earnings criteria for the "free" childcare support and tax free childcare. However I'm now nearly at the end of the 12 months and my earnings are right on the edge of being over the threshold.

When you renew your childcare eligibility you have to declare whether you'll earn more than £2,167 over the next 3 months (can be averaged if your earnings are seasonal) but to be honest, I dont know if i will. I'm hopeful but between unreliable childcare, kids illness and difficulties finding work I can't guarantee whether I'll earn enough over the 12 months to meet the earnings threshold.

So my question is:

If you claim the hours and tax free childcare but at the end of the 12 months you didn't earn enough, what happens? Do you have to pay it back?