What and how much to declare 1st qtr?

I am now in my 3rd yr as an auto-entrepreneur Macon and work has built up steadily for me to the point I was just over the limit last yr, but still within the tolerance. I have had a good run of work already this year and my projection for the first qtr is 11k as in work and monies completed. I have had a good deal of trouble with my back so I am planning on now taking it easy for the next few months and my annual projection will be around 25k.

However, I have an English client who has accepted my devis for 6k for works and although wants the work completed at some point this year wants to pay me 100% up front now. Apparently there is a tax break in the UK which finishes at end March which would enable him to offset all the work. So my dilemma is - If I declare all the monies recieved it would be close to 17k which I am imagining that I would recieve a letter stating that I could no longer be an auto-entrepreneur as I was slightly over last year and they would expect my income - based on the qtr 1 declaration to be substantially over.

So a good and thankful dilemma to be in - but I don’t want it to affect my whole work for the year by helping someone else offset some tax. What would your advice be - I have a cheque / invoice here that I can hold off until 1 April that would lighten it. The clear rules are you declare whatever income you have had within that window of Jan - end March.