“Didn't use to get” or “Didn't used to get”?

Opinions vary on this one. Here is a quote from Garner's Modern American Usage that explains why it should be didn't used to.

It shouldn't be written didn't use to, although this point has stirred up controversy among usage pundits. The argument goes that didn't supplies the past tense, and the main verb that follows should be in the present tense, as it is in a sentence such as "You didn't have to do that." But used to is an idiomatic phrase based on an archaic meaning of use (to be in the habit of). The form of the verb is fixed in the positive used to, and is unchanged in the far less common (and still less accepted) negative form, didn't used to.

It is interesting that if you look in google books for didn't use to, you get to page 3 before finding any real references- ones that don't occur in grammar books. When you look at didn't used to, there are seven real references on the first two pages. It seems that some grammar book writers have a little bee in their bonnet about didn't use to, but ordinary English speakers go for didn't used to.

Part of the problem is that didn't use(d) to is informal: in times gone by, it was not something that you would normally write down. And if you say used to at a normal speed, it becomes use-to: it is quite difficult to tell whether there is a d there or not.

The formal way of expressing this is used not to. This NGram is picking up lots of false positives, but examination of actual occurrences seems to show that used not to was, and still is, more widely used in writing than either form of didn't use(d) to. Here are some examples:

Our princes used not to dismiss ministers who served them well - Bishop Burnet's history of his own time (1818)

Mind you, I used not to be, either. How not to murder your mother (2010)

The original text was incorrect. You were right.

It's tricky for two reasons, I think.

1. In speaking, the d and t of "used to" merge into a single sound: /juːstuː/
2. "Used to" is a standard idiom that we very rarely analyse or rearrange. In reality, the "to" belongs to the object (an infinitive) of the verb "used", but we tend to see it as belonging to the "used to" idiom.

I used to get money

I did not use to get money

So let's take the "to [X]" away from "used to [X]", like so:

I used [snip]

I did not use [snip]

Clearly, "use" (not "used") is correct in the latter. Compare:

I used shampoo

I did not use shampoo

The phrase "used to" may seem as though it employs the verb "use" with an infinitive, but it doesn't really. Consider the following answers to the italicized questions preceeding:

• Where's the key you used to open the lock? Here's the key I used [to].

• Do you go there often? I used [to].

The former construction cannot accept the word "to" without a following verb (the answer could have included "to open it"), but the latter construction requires the word "to" even without any following verb.

The pronunciation of the idiomatic phrase "used to" in the second answer is different from the pronunciation of verb "use" followed by an infinitive, and such pronunciation would remain the same even in the construct "didn't used to". Since the positive construction combines the "d" in "used" into the "t" of "to" (so it's not really pronounced), it's not clear from pronunciation whether the negative form keeps the "d", but many native English speakers would be unaccustomed to having the word "use" be employed as a verb while being pronounced like the noun.

As has been pointed out by others, the "logical" argument for I didn't use to do that is that did already carries the verb tense, so it's not needed in used. Same as, for example, I didn't have to do that.

But as this NGram shows, usage has changed considerably over the past century and more...

Unsurprisingly therefore, you'll find plenty of traditionalist grammarians defending the older style (which is completely inaudible in normal speech anyway). But it's pretty obvious which version has the upper hand today, so I suggest you go with that unless you want to look like an old fuddy-duddy.

As pointed out by John Lawler in an ELU answer on this topic...

Both [spellings] look bad, the first because used looks like a misspelled infinitive,and the second because use to doesn't look like it sounds like used to should.
This should be considered a bug in the orthographic system.

The original text is valid. My dictionary lists "used to" as (1) "accustomed to" and (2) "... express habitual or accustomed actions ... taking place in the past but not continuing into the present".

See "The New Collins concise dictionary of the English language", 1985 edition.

"That's money in their pockets that they didn't used /use to get".

Only ".. that they didn't use to get" is correct. The uncertainty probably arises because "used to" is pronounced with a single /t/ and hence is homophonous with the "use to" in “they didn’t use to get”.

The aspectual verb "use" has no present tense, only infinitival and past forms, so although the form "use" appears to be a present tense form, it is in fact the infinitival form which is only used in negatives and with inversion: "they didn’t use to get"; "did they use to get"?

There is the added complication that "use" can be a lexical verb or an auxiliary one, though the books tell us that many speakers treat it as a lexical one. I suspect that’s due to the unacceptability for many people of the auxiliary use found in, for example, %"Smoking usedn’t to be allowed" and %"Used he to smoke"?

Lexical Use (infinitival verb-form and do-support required in negatives and questions):

"they used to get".

"they didn’t use to get".

"Did they use to get"?

Auxiliary Use (past tense verb-form, no do-support required):

"they used to get".

%"they usedn’t to get".

%"used they to get"?

(Note: % = grammatical in some dialects only)

The verb "used to" and the verb "use" are two different words with different meanings. To confuse the two and claim that to "used to" requires the infinitive form "use" because it follows "did" or "didn't" ignores the fact "used to" is a completely different word. I say that the construction "used to" is a word even though it appears to be two words,hence the confusion and the understandable desire to correct the past-tense-looking part of "used to", but the construction signaling "a habitual act in the past" to follow it never appears without the "to"; therefore I claim that the construction is together a word in its own right. "I used to use shampoo" and "I didn't used to use shampoo", for example, are correct if awkward sounding. And very different in meaning from "I used shampoo" and "I didn't use shampoo".

I wouldn't use those constructions in writing, except in dialogue. "I used shampoo when I was younger, but I don't use it now."

The original text was correct: the proposed 'correction' is incorrect.

"Used" is past tense, so it is needed here. It is so hard to say though, that the 'd' is often "swallowed" when spoken, so many don't even know it's supposed to be there.

Simple, remember when you use 'did' the verb should be in present tense.

So, "Did not use" is correct phrase.

Similarly ---

• I did not handle it properly--- (wrong: not handled)
• I did not give it to him ------(wrong: gave)

Neither: instead, change the target of the negation

Because "used to" is an idiomatic expression which does not, otherwise, reflect current usage over the verb "use" except when used atomically as such an expression (see @JavaLatte's excellent answer, including for the appropriate direct negation form), my usual recommendation is to avoid the controversy between whether or not to change the tense and instead to change the structuring:

Didn't used to get

easily becomes

Used to not get

This is also, in a sense, more overall correct. While "use" is a verb, in its idiomatic form it is not actually the main verb of the sentence. Instead, "get" is. "Used to" is instead an adverbial time marker that stands in for, essentially "in the past." It sets when they did or did not "get." So the negation applying to "get" is more appropriate.

Consider:

In the past they did not get it.

Versus:

Didn't in the past get it.

Hopefully the awkwardness if not outright incorrectness of the second phrasing by comparison to the first becomes more immediately apparent when using something other than the "used to" idiom. Personally, I find "didn't used to" along with "didn't used to" to both be similarly awkward, regardless of which one might be regarded as correct.

With this recommendation, the sentence would have improved in overall clarity:

That's money in their pockets that they used to not get.

I would also agree with the portion of @JavaLatte's answer covering "used not to," as it is definitely preferable to my ear and sense of structure than either of the forms using "didn't" if the intent is to negate the sense of past tense rather than the main verb of the sentence. But the related structuring is also, by degrees, relatively more archaic in tone.