Well, well, well.  If the land was sold in 2019 and the OP is trying to dig up a basis now, I think the client is in trouble.  I just thought they're somehow working on the 2016 return.

It sounds to me a F.3520 wasn't filed for 2016 when the property was inherited.  No tax would have been payable on the foreign bequest but the penalty would amount to 5% of the bequest for each month of failure to report, limited to a total of 25%.

The taxpayer may also have omitted to file a F.8938 if the inheritance was in a foreign estate and the max aggregate value of the SFFA exceeded the applicable threshold.