Help:Maintenance template removal
Overview: Maintenance templates (or "tags") are not removed automatically. Even if you fix the issue(s) described in a maintenance template, the tag will remain in the article until you or someone else manually removes it. The mechanics of removal are usually as simple as clicking "Edit" at the top of the page or in the section involved (if you're not already in edit mode), removing the code that produces the display of the template, leaving an edit summary, and saving the page.
It is not okay to remove maintenance templates until the issue flagged by the template is remedied first—that is, until the maintenance tag is no longer valid—unless it truly did not belong in the first place.
Wikipedia works because of the efforts of volunteers just like you, making bold edits to help build this encyclopedia. Fixing problems and then removing maintenance templates when you are done is important in that effort.

Addressing the flagged problem: We don't know which maintenance tag brought you to this page, and thus what specific problem needs attention. However, every maintenance template contains links to help pages, policies, guidelines, or other relevant pages that provide information on the problem the template was placed to flag. You will also find guidance on some of the more common templates below.
Many common templates address problems with article citations and references, or their lack – because reliable sourcing is the lifeblood of Wikipedia articles and at the core of all of Wikipedia's content policies and guidelines, such as notability, verifiability, neutral point of view, and no original research. But a host of other issues may be flagged, including tone and style of writing, structure, and formatting, lack of links to or from other articles, compliance with Wikipedia's manual of style and the lack of a lead section.
Please make sure the issue has been resolved before removing the template. That does require some effort on your part—to understand both the problem and how to solve it.

An example: If the issue flagged by the maintenance template is that the article contains no references, a citation needed template used might be {{Unreferenced}} –  typically placed by the code you would see when wikitext (source) editing: {{Unreferenced|date=September 2024}}.
It is important to understand that what you see when reading an article, and what you see when editing it, are different unless you're in Visual editing mode. Thus, the above code, only seen when doing source editing, results in the display of the 'called' template below:

This template contains several links, indicated by the words and phrases in blue. Three of these links are to pages that, when explored, provide context and resources for you to understand why the template was placed on the page, and how to address the issue of the article being unreferenced:

"cite", which links to the content guideline Wikipedia:Citing sources;
"sources", which links to the policy Wikipedia:Verifiability; and
"adding citations to reliable sources", which links to a help page providing a how-to guide to the basics of citing references.
Whatever maintenance tag brought you to this help page should likewise contain relevant explanatory links addressed to whatever its issue is. Read these explanatory and contextual pages to learn about the problem and what it is you need to do to take care of it. Again, some of the more common maintenance templates seen are addressed in the specific template guidance section below.

When to remove: Maintenance templates are not meant to be in articles permanently. Any user without a conflict of interest may remove a maintenance template in any of the following circumstances:

When the issue has been adequately addressed;
Upon determining that the issue has been resolved (perhaps by someone else);
If it reasonably appears that the template did not belong when placed or was added in error. Consider first discussing the matter with the original placer of the template (unless this user is no longer active on Wikipedia). In any case, if the issue appears contentious, seek consensus on the talk page;
When an article talk  page discussion has not been initiated (for templates requesting it);
When there is consensus on the talk page (or elsewhere) as to how to address the flagged issue, and you are reasonably implementing those changes. (It is good practice to note the location of the consensus in the edit summary accompanying your removal, ideally with a link to the location);
When it can reasonably be concluded that the template is no longer relevant, such as a {{Current}} template appearing in an article that no longer documents a current event;
If the maintenance template is of a type that requires support but is not fully supported. For example, neutrality-related templates such as {{COI}} (associated with the conflict of interest guideline) or {{POV}} (associated with the neutral point of view policy) strongly recommend that the tagging editor initiate a discussion (generally on the article's talk page) to support the placement of the tag. If the tagging editor failed to do so, or the discussion is dormant, and there is no other support for the template, it can be removed;
You may remove a template when according to your best judgment the lack of edits and/or talk page discussion should be interpreted as the issue not worth fixing (as a form of "silent consensus"). Please note there is currently no consensus for general age-related removal of maintenance templates – that is, removing a template purely or chiefly because it is old is not considered a sufficient argument. Exception: removing POV-related templates whose discussions have gone dormant is encouraged, as addressed in the bullet point immediately above;
Lastly, there are times when a person attempting to address a maintenance template that flags some fundamental matter may find that the issue cannot actually be addressed. For example, if an article is flagged as lacking citations to reliable, secondary sources, written by third-parties to the topic, and a user seeing the maintenance templates discovers that such sources appear not to exist, that usually means the article should be deleted. In such cases, it is not so much that the template does not belong and should be removed, but rather that flagging the page for maintenance will never address the more critical issue that the page itself does not belong on Wikipedia at all.

When not to remove: You should not remove maintenance templates if any of the following apply:

You do not understand the issues raised by the template;
The issue has not yet been resolved;
There is ongoing activity or discussion related to the template issue;
The problem that the maintenance template flags is plainly and unambiguously required for a proper article under Wikipedia's policies and guidelines;
You have been paid to edit the article or have some other conflict of interest [exceptions apply: see individual template documentation].

Removal: Have you carefully read the help pages and thoroughly fixed the problem? Or have you made a considered decision that the template is not, or is no longer, applicable? Great! Now, to remove the maintenance template:

Either click on "edit" or "edit source" at the top of the page, or if the maintenance template is not at the top but somewhere in the body of the article, you might instead use a section edit link;
If you are editing wikitext ("source" editing): Delete the template code. The template code you see in this edit mode will usually be in the following form, as in the example above: {{Name of template|date=Month Year}}.  If you are editing using VisualEditor: Click on the template (tag), which will then turn blue. Press the "Delete" or backspace key on your keyboard.
Leave a descriptive edit summary, e.g., "Removed [insert the name of template] because I have fixed the issue;"
Click Publish changes.
That's it. Thank you!

Changing a template: Problems flagged by some templates may imply secondary problems that will still exist after you take care of the main issue. In such cases, it may be more appropriate to switch the template to another applicable one following your edits, rather than just removing it. The reasoning behind the change in templates should be addressed in the edit summary.
A case in point is the {{Unreferenced}} template example used above. It is placed on pages with no references. Thus, adding just one suitable reference renders that maintenance template inapplicable. However, that change does not take care of the overarching issue of poor sourcing. In this example, a change to a different template may be appropriate, depending on the type, quality, depth, and manner of sourcing added to fix the issue, such as {{refimprove}}, {{No footnotes}}, {{Primary sources}}, or one of the many others listed at Wikipedia:Template messages/Sources of articles.
Conversely, some templates flag highly discrete issues where there is no need to consider a switch to another template. For example, if an article is "orphaned" – no other articles in the main article namespace link to it – then once that is taken care of (by the addition of links to it from other articles), the issue is gone entirely and the tag's removal is unambiguous. 
When a flagged issue has been addressed in parts of an article but remains in discrete sections, clarity may be served by replacing the template with a section variant, or by use of inline cleanup tags, if such versions of the template exist.
In some cases, it may be helpful to request a review of a maintenance template's removal or proposed removal with the editor who initially added it to the article at issue.

Specific template guidance: This section guides you on how to address some of the more common specific templates that may have brought you to this help page. More detailed information about the templates can be found by following the links to the templates themselves.
Click "show" at the right to display the instructions.

Researching the tagged issue: As noted previously, most templates contain links to guidance pages.