Most people think that the skill in Interior Design lies in creating stunning spaces. The truth is many people are capable of designing a stunning room. Experience in design will provide you with a lot of knowledge about ergonomics, fabric and furniture durability, range of products available etc, but the real skill (the expertise you are paying for) is transforming it from concept to reality. Managing your money and the logistics to get everything on to site at the correct time and in the correct order, and being fast thinking when something goes wrong and causes a ripple in the supply chain. And doing this comfortably within your budget.
It's all very well looking at a nice sofa and saying - "yes that one but in a green fabric." Behind the scenes, that means ordering the fabric, having it sent to a fire retardant company to be coated to meet current regulations, having it then shipped on to the furniture supplier, usually with trim sourced from somewhere else. If you have matching cushions, those are usually made somewhere else as well and will require cushion inserts which have to be purchased and sent independently. So to calculate the cost of your sofa before it has even been bought, you have the sofa cost, the fabric cost, the coating cost, the trimming cost, the cushion inner cost and 5 different delivery costs. And you will need to separate out the VAT. That's a lot of figures to juggle, and if you were using spreadsheeting software you'd be flicking through tabs to cross-reference all day long.
Serval software programs exist for the interior design trade, king among them is Estimac.
EstiMac allows you to control the financial and administrative aspects of a project. They claim that it's "simple and efficient, leaving you more time for creative work". I think we'd probably argue against simple, it's not very intuitive, but once you've mastered it it is certainly very efficient. It's a time consuming part of the business anyway, but having everything in the one place does make it easy to collage and access data. We find the need to save multiple copies, as if a client changes their mind you need to completely erase the data, and it wouldn't be stored anywhere else (as the point of it as it is a centralised system) so we need to have a back up incase the client wants to go back to an original item (happens quite often).
EstiMac handles all your project information including descriptions, images, confidential details, costings, markups and fees. It uses this information selectively to generate client estimates, invoices and statements, supplier orders, contractor listings, management reports and summaries. It's super handy at detecting anything that hasn't been entered correctly, so it limits human error style mistakes, and having a penny accurate display of how much you have spend and how much you have left makes projects run very smoothly.