I heard this phrase in the current movie "The Post" and suspect it is an anachronism. Was this phrase in use in 1971?
My first instinct would be that this is quite an old expression, although it was likely used in a military or otherwise ranked and graded environment. It may be a bit more recent than I thought though. I found this link on quoteland.com where user thenostromo cites a source that is, alas, no longer available. It is however, archived by the WayBack Machine - thank you @DanBron for the link!:
The oldest use of "above my paygrade" only dates to 1999 on google news archives, from a chat transcript with gossip writer Lloyd Grove. However, searching for "above my pay grade" with a space yields older sources, going back to a 1981, which appear to have a military origin. In 1981, it came from a quote from Navy Secretary John Lehman in a UPI story.
Quote: “There has been no decision on Admiral Rickover’s extension (in the job) and it really is a decision that is above my pay grade" ~ Navy Secretary John Lehman
Its use by a military pilot in 1986 at least received notice by one columnist. It continues to be mentioned most often in military settings until the early 1990s, when it began to be more broadly used by US government officials. In July 1996, USAtoday described US republican congressperson Susan Molinari as someone who "uses hip phrases like above my pay grade and totally iced."
So that would indicate an early '80's origin of the expression, making your '71 quote indeed anachronistic.
However, another user, Bobby Stafford, on the same page quotes from personal experience:
I spent 20 years in the U. S. Army, beginning in 1966. I heard that phrase almost from the beginning, perhaps even once or twice in basic training. For those not familiar with the difference between 'rank' and 'grade': Rank is a titled designation, such as 'private' or 'sergeant.' Grade is actually for 'pay grade.' Enlisted soldiers grades range from E1 to E9, with equivalent ranks being private, corporal/specialist, etc., through Sergeant Major.
More than once I would ask a superior what a certain decision would be, and he would say, "That's above my pay grade." Meaning, of course, "I don't have the rank to make those decisions."
It's a military cliche I've heard for over 45 years.
So, if you trust this person, the expression has at least been in use since 1966, albeit in a military context. Whether your '71 quote is an anachronism would then largely depend on the context in which it was used.
Marlon M. Hanks, in 1955, takes the cake (so far) for performing beyond her pay grade:
...clerk-typist in the Supply & Fiscal Department, U.S. Naval Construction Battalion Center, Port Hueneme, is the winner of a $100 Superior Accomplishment award for performance of duties far beyond her pay grade and assignments.
This should not come as a surprise; women routinely perform far beyond their pay grade.
For above the pay grade, a 1958 use is the earliest I've found so far in the particularized (to individuals or specfic groups of individuals) sense of "above one's level of professional responsibility" (OED):
At an advanced base no man can expect to be limited to the duties outlined for his billet. He may have to do some work that is above his pay grade, and he may, just as often, have to take on dull tasks and do them cheerfully.
Uses of the phrase "above ... pay grade" in a generalized sense are fairly common in the 1940s and 1950s in military contexts. For an example of such use in a generalized sense, this from 1940:
With the automatic pay raise, the applicant accepting enlistment is assured that at least after four months of service his pay will jump to $30 per month. His promotions above that pay grade are left almost entirely up to the man himself.
By the 1970s, the phrase in the particularized (to individuals or groups of specific individuals) sense is well-established in military contexts.
The earliest instance I've been able to find is 1977, but that doesn't mean that the expression wasn't already part of military jargon well before then, merely that this documents early use by military personnel testifying before Congress.
A Google NGram shows a steep upward trend in the early 1980s, but a decline shortly before the turn of the century.
The OED records it from 1981 (Aviation Week & Space Technol. 18 Apr. 13/3) "When asked about the delay on the mobility study, Huyser said, ‘That's above my pay grade at the Defense Dept. Our contribution on it is complete’", so it's not unbelievable that it could have been in use ten years earlier. That example is clearly literal - I don't know if the use you are asking about is literal or not.
The phrase "Pay grade" is exemplified from 1883.
COHA is no help, as it has only one instance of "Above * pay grade", and that is from 2009.
The Farlex Dictionary of Idioms, dedicates an entry to
beyond (one's) pay grade
1. The responsibility of those who are of a higher authority than oneself, denoted by the level of pay which one receives in comparison to one's superiors.
2. Above or beyond one's skill, knowledge, ability, or willingness to participate.
The following examples seem to match the first meaning, they have already been mentioned in the comments, but I'll include the snippets and the sources.
Mr. Fine. Considering our early warning capability, the examples you have described are not ones that you realistically would ever expect to occur, am I correct?
Colonel Coy. Are you saying, sir, that if we would, in fact, perceive a massive attack coming that we might launch from under that attack?
Mr. Fine. Yes.
Colonel Coy. Sir, I think that is a policy decision only the President can answer. That is beyond my pay grade.
1969, Congressional Record Proceedings and Debates of the ... Congress
Mr. SIMS. Would your proposal involve a reduction in the present taper of the fare structure? Mr. WISER. That is beyond my pay grade, I am sorry.
Mr. WILSON. No, it would not. How the taper came out would depend on how, at individual distances, the markets were weighted by density. Our calculations based on 1967 data showed there would be increase in taper which is in accordance with your expectations.
As Dan Bron notes in a comment beneath the posted question, and as KarlG reiterates in a separate answer, one fairly early match for "above [one's] pay grade" in the sense of "at higher level in the hierarchy than [one's] own is "Fiscal Year 1978 Authorization for Military Procurement, Research and Development, and Active Duty, Selected Reserve, and Civilian Personnel Strengths: Hearings Before the Committee on Armed Services, United States Senate, Ninety-fifth Congress, First Session, on S. 1210 (1977):
Senator [Dale] BUMPERS: Who makes the final decision on whether Iran is going to get F14's and Phoenix missiles and so on?
Mr. ALLEN: Somebody way above my pay grade.
The idiomatic use of "beyond [one's] pay grade" to mean above my level of skill or competence or decision-making authority goes back at least to the 1969 and 1971 instances first cited by muru and Phil Sweet, respectively, and subsequently compiled in Mari-Lou A's useful answer. My impression is that this expression and "above [one's] pay grade" are identical in their idiomatic meaning and may be used interchangeably, although an Ngram graph for 1950–2008 of "beyond my pay grade" (blue line) versus "above my pay grade" (red line) indicates the latter is the more common form.
The explicit association of pay grade with skill level (and so, implicitly, with level of competence and authority) in U.S. military jargon has roots that go back at least to 1954, when skill levels and pay grades appear as part of the standard nomenclature for categorizing job qualifications and appropriate salaries, as in U.S. Department of the Air Force, "Enlistment and Reenlistment in Regular Air Force" (1954). The two terms come together no later than in U.S. General Accounting Office, Decisions of the Comptroller General of the United States (1959):
Under section 209, an enlisted member may be awarded proficiency pay if he is found to have "special proficiency in military skill." This is interpreted as requiring a finding that the enlisted member either (1) is fully qualified in a critical military skill in the pay grade and skill-level in which he is serving, or (2) has demonstrated outstanding effectiveness in an assigned skill irrespective of its criticality. In this connection, it should be noted that in the armed forces the term "military skill" refers to a specific military specialty and skill-level within that specialty. Each skill-level normally has a direct counterpart in terms of military pay grades.
So it is easy to see how even in the late 1950s military personnel might equate skill level with pay grade and use the terms (loosely) interchangeably. As for the issue of a task or responsibility or decision-making power being above an individual's skill level or pay grade, consider this excerpt from Edward Frederickson, U.S. Army Research Institute for the Behavioral and Social Sciences, Assessment Alternatives for a High Skill MOS: Final Report (1975) [combined snippets]:
Usually skill level correlates with pay grade. However, an individual may be awarded a skill level above his pay grade, but not below. This, in essence, indicates that an individual must be skill-qualified before he is awarded a promotion in pay grade. MOS [Military Occupation Specialty] and skill level qualifications are evaluated periodically using interviews, MOS evaluation tests, and performance appraisals and ratings. Decisions that can be made following these periodic evaluations are that the individual continue in his career progression, that he be reclassified to a lower skill level in the MOS, or reclassified to another MOS.
This excerpt indicates that the U.S. military made a serious, systematic effort to maintain a fundamental connection between pay grade and skill level. Although a soldier might on occasion be advanced to a skill level above his or her current pay grade (but not vice versa), the military's working assumption was that the pay grade would eventually catch up with the skill level. Here again, the practical connection between skill level and pay grade invites treating skill level (that is, competence and hierarchical authority) and pay grade as synonymous ideas and of using the latter term to stand for the former.
Thus, when U.S. soldiers or other military persons (and later, other government workers and private-sector workers) say that something is "above my pay grade," they may simply be saying that the thing in question falls into the purview of persons higher in the hierarchy than them—and thus at a different skill level or decision-making authority than theirs. And the examples of the idiomatic use of "above my pay grade" from 1960 and 1971 establish beyond reasonable doubt that it would not have been anachronistic for a character with a military background to say in 1971 (as the script of The Post has someone do) that something was above someone's pay grade.
"Above my pay grade" goes back to least
Google books had wrong date...
General Johnson: Mr. Congressman, we have an expression in the Marine Corps. I think you just asked me a question above my pay grade.
Mr. Dan Daniel: I was going to suggest you let Mr. Webster respond to that one.