This all I could get out of them when asking about their handling of bitcoin taxes. I am guessing they don't send anything unless you sell on their app, but I have yet to get any concrete information on this.
a 1099-B only pertains to taxable transactions, generally sales. there would be nothing to list if you didn't sell through their app so i assume if you
only buy that you won't get one.
this is different from coinbase, kraken, etc who send out 1099-K forms. with them, you can conceivably pass the 200 transaction + $20k threshold just by buying. then you will receive a 1099-K.
Cash App does not report a cost basis for your Bitcoin sales to the IRS.
at the cost of convenience, that at least means you don't have to correct their mistakes or worry about them exaggerating your gains to the IRS.