Released on Apr 14, 2016, It is a Major Upgrade. This version is built on .NET 4.5 according to the new instructions from PayPal. https://www.paypal-knowledge.com/infocenter/index?page=content&id=FAQ1914&expand=true&locale=en_US Based on this instruction, to avoid any disruption of service, you must verify that your systems are ready for this change by June 17, 2016. This version uses TLS 1.2 which requies .NET 4.5. You should upgrade to this DLL in order to avoid any disruption of services. We tried our best not to retarget our control on .NET 4.5, rather we searched possibilities to use TLS 1.2 using earlier versions of .NET like 3.5, but looks like it is not possible. Here is another MSDN social link which confirms this impossibility. https://social.msdn.microsoft.com/Forums/vstudio/en-US/cce555cc-cf23-4ad2-8a3b-0bc49cc17349/tls-12?forum=netfxbcl