NATA does not provide accreditation for ultrasonic test on fillet welds.
Also, there is no Australian standard that specifies how to perform UT on a fillet weld.
AS 2207, an ultrasonic test method standard also does not cover Fillet welds in any of the normative sections.
Although, there is an International standard on UT on FW’s there are several restrictions to the test method.

My belief is UT can be performed on almost everything. We only need to be aware of test restrictions to obtain fruitful results by applying appropriate technique and spending adequate resources (time and money). AS 2207 Appendix F (Informative only) states that “ UT on FW is usually restricted to either a general assessment of weld quality or an examination for a specific anticipated discontinuity. FW in plate thickness less than 10mm will require preparation of special procedures.”

Hence LMATS can perform UT on a FW but cannot issue NATA endorsed report.
LMATS will not guarantee that all defects can be detected by UT especially LOF. (Because ultrasound may not reflect to the transducer due to the angle of the defect).
LMATS may be able to find gross discontinuities such as centre line crack, slag inclusion, etc.
FW are generally used where BW cannot be reasonably achieved. Thus, generally there are restriction to access FW for UT. (Not enough space to place transducers)

A specific weld coupon having anticipated discontinuity will need to be produced by the manufacturer and then tested by LMATS to ensure that the anticipated discontinuities can be successfully detected using the prepared UT procedure.

Please contact LMATS  for any other information or assistance.