The correct usage of past tense with just

I understand that phrase:

"I have just bought a house".

is correct.

But I also saw, that sometimes people could say:

"I just bought a house."

Is it correct?

Solution 1:

The use of temporal just with a Perfect construction evokes the Hot News! sense of the Perfect.

This sense is almost always used for recent events of great importance. Generally the Past is OK, too.

• Botswana has just invaded Uruguay.
• Botswana invaded Uruguay this morning.

In the case of the original examples, the event is certainly important enough

• I've just bought a house.
• I just bought a house.

but there is no real difference in meaning or use, no grammatical or semantic distinction, between the two. Although certain sentences sound odd with one or the other form, because of irrelevant restrictions on individual constructions.

Different speakers with different habits and experience will probably see potential distinctions to make, but nobody will see or make the same ones. When either choice is OK, a speaker chooses the one that sounds best to them, for whatever reasons they may have.

Solution 2:

In my idiolect, as for many speakers of British English, the simple past is incompatible with temporal just: I would say I have just sold a house but not I just sold a house.

For many (?most) speakers of American English, and increasingly in Britain as well, I just sold a house is grammatical.

As others have said, there is another meaning of just ("only", "merely") which is compatible with either tense.

[I changed "bought" to "sold" because I have, in fact, just sold a house].