Kettering’s Lower Street Post Office is likely to be affected by Saturday’s strike action.
The branch is one of 300 nationwide set for disruption in the walkout, although it is not yet clear how badly it will be affected.
Kevin Gilliland, Post Office group network and sales director, said: “The vast majority of our directly managed branches were open for business during strike action earlier this week.
“However, we are reminding customers who need to access any of our services before Christmas that all our branches will be open for business as usual on Thursday and Friday.
“Although many of our around 300 directly managed branches will be open on Christmas Eve, some will close at 12.30 or during the afternoon in line with their normal Saturday opening hours.
“All of these branches will close by 4pm.”
A Post Office spokesman said they would not know the extent of any disruption for certain until the day of the strike.