Should I return deposit or register it late??

Hi all

I stupidly forgot to register one tenant's deposit. She's now moved out and there are a few things to charge her for. We haven't gotten to the details yet but I went to check her deposit and realised I hadn't registered it. i want to do right by her but also hoped she could contribute to the cost of cleaning as per her inventory.

Anyway, at this stage is it better I register it late with DPS or offer to repay it in full? It's only £180.

Thanks

Sean