Many speakers of English in non-English speaking countries often use 'SHOULD HAVE TO' in speaking and writing. Among them, sentences like the following are very common.
1) “I SHOULD HAVE TO complete my assignment within three days”
2) “You SHOULD HAVE TO pass this test”
But, according to English grammar, this is a wrong use. Instead of using SHOULD HAVETO, you must use either SHOULD or HAVE TO. The reason is SHOULD is almost equal to HAVE TO although there is a slight difference in detailed grammatical analysis.
So, the previous wrong sentences can be rewritten as follows:
1) “I SHOULD complete my assignment within three days”
OR
“I HAVE TO complete my assignment within three days”
2) “You SHOULD pass this test”
OR
“You HAVE TO pass this test”
You can also express the same idea by using ‘WILL HAVE TO’ as in,
“I WILL HAVE TO complete my assignment within three days”, “I WILL HAVE TO pass this test” etc.
1) “I SHOULD HAVE TO complete my assignment within three days”
2) “You SHOULD HAVE TO pass this test”
But, according to English grammar, this is a wrong use. Instead of using SHOULD HAVETO, you must use either SHOULD or HAVE TO. The reason is SHOULD is almost equal to HAVE TO although there is a slight difference in detailed grammatical analysis.
So, the previous wrong sentences can be rewritten as follows:
1) “I SHOULD complete my assignment within three days”
OR
“I HAVE TO complete my assignment within three days”
2) “You SHOULD pass this test”
OR
“You HAVE TO pass this test”
You can also express the same idea by using ‘WILL HAVE TO’ as in,
“I WILL HAVE TO complete my assignment within three days”, “I WILL HAVE TO pass this test” etc.