I’ve seen occasional grammar guides arguing that it’s technically incorrect to use “ter que” to indicate obligation. For example in “101 Erros de Português que Acabam com a Sua Credibilidade” by Elsa Fernandes, she says “Ultimamente tem-se vulgarizado o uso da construção *ter que* para significar obrigação […] os especialistas indicam que, nesse caso, a forma mais correta é ter de.”
This ciberduvidas article makes the same point
But this morning I was reading through (and trying to memorise) Mar Português by Fernando Pessoa and I noticed it has this couplet
Quem quer passar além do Bojador
Tem que passar além da dor
This looks like the great man is using tem que in exactly the way “os especialistas indicam” is wrong. Borrowing a phrase we sometimes use about Shakespeare, “I’d rather be wrong with Fernando Pessoa than right with Elsa Fernandes”, but I asked on Reddit to see if anyone else had thoughts on what might be going on. After all, the poem also includes an old-fashioned spelling of the words “rezaram” and “nele”, so maybe the language has drifted a bit since his day. It doesn’t seem so though.
“Ter que” is used a lot in Brazil, and as Elsa says, its increasingly common in colloquial speech in Portugal too. It’s technically wrong but seems to be one of those things that is used a lot. If teenagers and Fernando Pessoa are using it then it’s probably safe to call it a de facto standard. Best avoided in exams, but it seems as if it would be pedantic to pick someone up on it in normal conversation.
So what is “ter que” supposed to be for? It’s quite similar but it is more to do with ownership than obligation. So “tem muito que contar” means “he has a lot to tell”. In other words, he has a lot of experience, he’s an interesting guy. As opposed to “tem de contar muito” which means he’s obliged to tell you a lot.
Tenho muito que fazer = I have a lot on my plate
Tenho de fazer muito = I am being forced to do a lot
I had a complaint about the low quality of the pun in the title, so if you prefer you can think of it as “Ter Que’s Voting For Christmas”