A common question is whether PLC programming and control development can qualify as research and development for the federal R&D tax credit under Section 41. The short answer is that PLC programming and control development may constitute qualified research when the work evaluates alternative approaches to resolve a technical uncertainty about control performance. Routine PLC programming for known applications generally is not qualified research. This page explains the framework in general terms. It is educational and is not individualized advice. For the foundational framework, see our page on qualified research.
When PLC Programming May Warrant Review
PLC programming and control development may warrant review when the work involves a genuine technical uncertainty and a process of experimentation. Under the four-part test, the work must be for a permitted purpose, be technological in nature, be intended to eliminate uncertainty, and be conducted through a process of experimentation.
Common scenarios that may warrant review include:
- Control sequence development — evaluating alternative control sequences to resolve uncertainty about whether a PLC program can achieve the required process performance.
- Timing and synchronization — testing alternative approaches to resolve uncertainty about whether a PLC can synchronize multiple operations at the required speed.
- Fault handling development — evaluating alternative fault-handling approaches to resolve uncertainty about whether a PLC can detect and respond to the required fault conditions.
- New process control — testing alternative control approaches to resolve uncertainty about whether a PLC can control a new process to the required performance.
Routine Programming vs. Control Development
A central distinction is between routine PLC programming and control development:
- Routine programming — writing PLC programs for known applications using established logic and known sequences. There is no technical uncertainty about whether the program will work. This is production programming, not research.
- Control development — developing new PLC logic where there is a technical uncertainty about whether the control can achieve the required performance, and evaluating alternatives to resolve that uncertainty. This may warrant review.
Hypothetical Example
Consider a manufacturer that is developing a new PLC control system for a new process with complex sequencing requirements and is uncertain whether any available control approach can achieve the required cycle time and quality. The company evaluates alternative control sequences, tests each, and systematically varies the approach to resolve the uncertainty. This systematic evaluation of alternatives may warrant review as qualified research.
By contrast, if the same manufacturer writes a standard PLC program for a known conveyor control application, that is routine programming, not research.
This example is illustrative only and does not state that the activity definitely qualifies.
Documentation That May Help
Records that can help support PLC programming claims include control design records identifying the uncertainty and alternative approaches, control-performance test results, and records of how results informed programming decisions. For more, see our page on R&D tax credit documentation.
Key Takeaway
PLC programming and control development may constitute qualified research when the work evaluates alternative approaches to resolve a technical uncertainty about control performance. Routine PLC programming for known applications generally is not qualified research. Because the distinction is fact-specific, professional review is appropriate before claiming the credit.