Cohen did no legal work for Trump in 2017 and there was no retainer agreement.
"Importantly, McConney admitted on the stand that Cohen was receiving $360,000 back on a $180,000 expense. He also admitted he was unaware of any other instance where an expense reimbursement would be doubled to account for taxes. Here was the exchange with prosecutor Matthew Colangelo:" https://statuskuo.substack.com/p/grossing-up-and-grossing-out
Grossing Up and Grossing Out

A day of receipts and lurid testimony in Trump’s criminal trial

The Status Kuo