The best app for interior designers depends on studio size. Large firms often want full procurement and accounting suites. A one- or two-person studio usually needs the money side done well: retainers, deposits before orders, clear invoices and a place to share boards with clients that is not buried in a long email thread.
A furniture procurement deposit protects your cash flow more than any other habit. Bill the client with the spec sheet attached, wait for payment, then place the order. You stop covering a custom sofa on your own card while production takes ten weeks.
Clients trust an interior designer invoice they can understand. List the tasks, attach the hours summary, and send it on the same day each month. For ongoing clients, a monthly design retainer on Team or Pro plans keeps the work moving without a new invoice each time, and reminders follow any bill that stays open past its due date.
Smaller offers fit too. Sell an e-design package or a color consultation through a fixed-amount link, and collect the interior design contract signature on the client's phone before the first board goes out. Everything stays on one client profile.