Yes there is a transaction minimum that Stitch Express can process.
The minimum amount is R5 to be able to process a payment.
This is important to remember when using Stitch Express's products, like Payment Link or Plugin.
However, there is no upper limit for a transaction. Important to note though, is while Stitch imposes no upper limit for a transaction your customer's bank or card provider may have certain limits in place.
If they are unable to complete a large payment, ask them to check the limits with their bank/card provider first.