Export Services without LUT - Goods and Services Tax - GST

Dear experts, our client is providing export services wef August 2023 filing returns with Nil tax.So far LUT has not been taken.If we take LUT now then whether we will get zero rate benefit for the amounts received so far. If not then whether we need to deposit 18% GST on the Export services provided then to apply for refund further how to deposit the tax, through DRC-03 /3B of subsequent month.Plz guide.